News in 5: Teen dies training for fight; Woman charged with partner's murder; Kids' dental health.

1. An 18-year-old was training for a martial arts event when she collapsed from dehydration. She died four days later.

On November 10, 18-year-old Jessica Lindsay was out for a run, in a last-minute attempt to 'cut' weight before an amateur Muay Thai fight.

The Perth teenager collapsed from severe dehydration, and was rushed to hospital. She passed away four days later.

Lindsay - who had been fighting in the ring for less than two years and was meant to fight the day after she collapsed - was running to ‘cut’ her weight down to meet the fight weight class of 64kg.

Weight cutting is a very rapid - and dangerous - method of losing weight in the lead up to an athletic event.

Most professional athletes are highly supervised during the process, which can involve decreasing water consumption, restricting meals and taking hot baths and using saunas. Lindsay's death has now raised questions about the safety of the sport.

Despite writing on Instagram that she felt "fit and healthy" in the lead up to her death, GP Dr Joe Kosterich told 9 News that there is a "point of no return" when it comes to heat exhaustion and dehydration.

"It is quite extreme," he said of the body's reaction to weight cutting.

"People may choose to ignore the warning signs because they're focused on what they're trying to achieve and it's an issue for amateurs.

"Professionals will be coached, they will be monitored."

Lindsay's death will be investigated by the coroner, and a GoFundMe page has been set up by a friend to help her family cope with the loss.

"[Lindsay] was and still is a bright star that touched so many lives," the page reads.

"She always put other people first and her caring nature and positivity in life will never be forgotten. She was surrounded by family and friends till the end.

"Her legacy will make a change and stop this from happening to anyone else."

2. The widow of a wealthy NSW sheep farmer found dead three months ago has been charged with his murder.

The partner of a NSW sheep farmer who died three months ago has been charged with his murder, AAP reports.

Matthew Dunbar, 42, was found unresponsive at his home in Walcha, on the state's northern tablelands, in the early hours of August 2.

Paramedics were called to the property, Pandora, on Thunderbolts Way but he wasn't able to be revived.

Police have treated the death as suspicious and set up a strikeforce to investigate Mr Dunbar's death.

On Saturday morning, detectives arrested Mr Dunbar's partner Natasha Crossman and took her to Tamworth police station for questioning.

About 12 hours later, police confirmed she had been charged with murder.

Crossman had previously said her "kind and sweet" partner took his own life, and said the death had left her with post-traumatic stress syndrome.

According to The Daily Telegraph, police will allege Crossman attempted to buy ram sedatives from the local vet in the days before her partner's death.

A staff member refused to sell the tranquilliser to Ms Crossman as the pair didn't own any rams.

She appeared at Tamworth Local Court yesterday where she was formally refused bail.

3. Tony Abbott's daughter Frances is engaged... after meeting her partner just two weeks ago.

HEY FEYONCÉ ???????????? Two weeks was all it took to know that forever with you was a mighty fine idea @samloch ❤️???? #engaged #feyoncé #crazyinlove #helikeditsoheputaringonit #allthebeyoncehashtags #whywait #letsdothis #lovelovelove #allthemushystuff

A post shared by Frances Abbott (@notanotherfitnessblogger) on Nov 18, 2017 at 10:06pm PST

The 26-year-old daughter of former Prime Minister Tony Abbott, is engaged to former Olympian Sam Loch.

In a surprise announcement via Instagram, fitness model and Pilates instructor Frances Abbott wrote, “Two weeks was all it took to know that forever with you was a mighty fine idea. #engaged #feyoncé #crazyinlove… #whywait #letsdothis.”

The pair appear to have kept the relationship tightly under wraps until now, with Abbott referring to herself as “very, very single” in an interview published in the current issue of Harpers Bazaar.

Loch, 34, is a professional rower who has competed for Australia at the Beijing and London Olympic Games, placed second at the 2015 World Indoor Rowing Championships and holds several international Ergometer records.

4. More than 3000 Queensland kids are admitted to hospital every year for tooth decay.

Shocking new data shows that thousands of Queensland children are being admitted to hospital each year with rotten teeth.

The figures show that half of all hospital visits for tooth decay in the state are for children aged up to nine years old, The Courier Mail reports.

Children are required to be admitted to hospital when tooth decay becomes so bad the only solutions are multiple extractions or "very large fillings".

Tooth decay is a preventable disease, Australian Dental Association Queensland chief executive Professor Ian Meyers said, and is caused in large part by a diet that consists of "too much sugar".

Even the decay of 'baby teeth' can be detrimental to a child's future dental health.

"If [baby teeth] get very bad decay or have to be extracted early on, it can change the whole development of that child's teeth," Professor Meyers said.

Children should brush their teeth twice a day with fluoride toothpaste, avoid sugary drinks, have regular dental checks and eat a healthy diet to prevent tooth decay.

5. Music legends are mourning the death of 64-year-old AC/DC co-founder Malcolm Young.

AC/DC co-founder and guitarist Malcolm Young dies at 64 https://t.co/KAzsjilYfj pic.twitter.com/M8meoscsRd

— CNN (@CNN) November 19, 2017

Jimmy Barnes and Keith Urban both say AC/DC's Malcolm Young is the best rhythm guitarist they've ever seen, as tributes flow in for the Australian music icon, who has died aged 64.

Young, who was known for the powerhouse riffs and rhythm guitar that propelled the Sydney group to world superstardom, died on Saturday after a three-year battle with dementia.

Australian rocker Barnes said Young was "the greatest rhythm guitar player ever" and extended his condolences to his brother and fellow AC/DC star Angus Young.

"What a sad day for music," Barnes posted on Twitter.

Australian country music star Urban said he was "devastated" by Young's death.

"For me personally, the GREATEST rhythm guitarist of ALL TIME," Urban tweeted.

"Thank you Malcolm for all of the spit and fire, passion, ferocity, gravitas, and for the eternal inspiration."

Eddie Van Halen is among a large cohort of international rock greats who have also paid homage to Young online.

"Malcolm Young was my friend and the heart and soul of AC/DC," Van Halen said.

"I had some of the best times of my life with him on our 1984 European tour. He will be missed and my deepest condolences to his family, bandmates and friends.

Others who remembered Young are Black Sabbath's Ozzy Osbourne, Motley Crue co-founder Nikki Sixx, Rage Against the Machine axeman Tom Morello and KISS frontman Paul Stanley.

Young died peacefully on Saturday with his family by his bedside, a statement from the family said.

6. Top US General says he would refuse Donald Trump's order to launch "illegal" nuclear weapons.

US nuclear chief to resist 'illegal' presidential strike order https://t.co/XXQWDZe5rq

— BBC News (World) (@BBCWorld) November 19, 2017

The top US nuclear commander says he would resist President Donald Trump if he ordered an "illegal" launch of nuclear weapons, AAP reports.

Air Force General John Hyten, commander of the US Strategic Command (STRATCOM), told an audience at the Halifax International Security Forum in Nova Scotia, Canada that he had given a lot of thought to what he would say if he received such an order.

"I think some people think we're stupid," Hyten said in response to a question about such a scenario.

"We're not stupid people. We think about these things a lot. When you have this responsibility, how do you not think about it?"

Hyten, who is responsible for overseeing the US nuclear arsenal, explained the process that would follow such a command.

As head of STRATCOM, "I provide advice to the president, he will tell me what to do," he said in his remarks, retransmitted in a video posted on the forum's Facebook page.

"And if it's illegal, guess what's going to happen? I'm going to say, 'Mr President, that's illegal.' And guess what he's going to do? He's going to say, 'What would be legal?' And we'll come up with options, of a mix of capabilities to respond to whatever the situation is, and that's the way it works. It's not that complicated."

Hyten said running through scenarios of how to react in the event of an illegal order was standard practice, and added: "If you execute an unlawful order, you will go to jail. You could go to jail for the rest of your life."

The Pentagon did not immediately respond to a request for comment on Hyten's remarks.

They came after questions by US senators, including Democrats and Trump's fellow Republicans, about Trump's authority to wage war, use nuclear weapons and enter into or end international agreements, amid concern that tensions over North Korea's nuclear and missile programs could lead to hostilities.