In April, doctors discovered a neuroblastoma tumour in her abdomen.
Hazel and her mother Lauren have been staying at Children's Hospital Los Angeles during her treatments and Lauren admits they've been going a little stir-crazy. To pass the time, they've been taking walks, colouring in, play with Play-Doh, dressing up, getting creative with Hello Kitty tattoos …
Earlier this month, Hazel was admitted to the hospital with a fever. Her grandmother came to visit and told her about a funny sign someone put in the window of her hospital room when she was a girl. Hazel decided she wanted a sign too.
Together they stuck up letters with medical tape, saying "Send pizza RM 4112". "The nurses, doctors, other children and we all had a great time with it and thought it was just something to brighten someone's day."
"This sign was up for several days without even a single phone call asking to send up a pizza (which we completely expected!). Then, on Saturday, it all changed ..."
A man drove by the hospital and saw the sign. He took a photo and posted it on Reddit with the caption: "Photo taken outside Children's Hospital in Los Angeles. Smart kid."
Another Reddit user quickly responded, saying "No need to fear! Pizza Delivery will soon be here!" Lauren's father-in-law was keeping Hazel company when the delivery arrived.
And the pizza deliveries from Reddit users just kept on coming - over 20 arrived before the hospital said it couldn't handle any more. Hazel's mum rushed to the hospital and invited their fellow patients and families to join them for a pizza party.
Lauren's mum is hoping that sharing hope that Hazel's story helps spread awareness of childhood cancer. "We can use this opportunity to let people know that not enough research goes into how to treat our kids," she says.
She adds: "We don't take time for granted. We have four kids, 6 and under. [With little kids who] require attention, you forget to savor the little things. We’ve learned to take every moment and savor it and not wait to say things."