31-year-old blogger Heather Croxon has died after a tragic car accident.

Blogger Heather Croxon – who reviewed books on her blog Bits & Books – has died in a Sydney hospital, five days after she was hit by a car while walking on a footpath.

The 31-year-old had just bought a coffee from a local cafe when she was struck by the Toyota sedan outside the popular Chatswood Chase shopping centre last Friday morning.

Heather suffered critical head injuries in the accident, and was rushed to Royal North Shore Hospital's intensive care unit.

"Unfortunately things don't always work out the way we planned," Heather's sister, Amanda, wrote online.

"Today I said goodbye to my beautiful big sister who, as I held her hand, she took her last breath and passed on peacefully."

A number of friends that Heather had also met online through her blog posted heartbroken tributes to their friend.

"Heather's kindness, humour, and reliable presence meant so much to me," Shaina Coogan wrote.

"It doesn't feel real that she's gone, and I'm having so much trouble understanding why, beyond the fact that there's no reason why.

"She was so loved, and all I wish was that I'd told her so more often. My thoughts are with her, her family, and everyone else she touched, even if just through her words on a screen."

It is believed police are investigating whether the 67-year-old man who was driving the car that hit Heather had suffered a medical episode before the crash.

The car also struck a mother and her pram, but both were unhurt in the accident.