Corpse Girl’s nanites revived her

“They ended up in her body, and they started multiplying and fixing things. Maddy got older, became athletic, and they supported and enhanced her whole system. If anything went wrong—muscle tears, injuries, whatever—the nanites would zoom in, multiply, and replace it until her own systems could catch up.”
“And then she died,” said St. George.
The doctor nodded. “And then she died. And they tried to fix it.”
They looked at the spiderweb on the screen.
“From what you and the captain have told me,” continued Connolly, “she was probably mangled, missing a lot of tissue mass. So the nanites did what they’re supposed to do. They replaced the damaged and missing sections. And they kept replicating and replacing until they made her whole again. But the body was decaying, maybe getting eaten by scavengers. It was an uphill battle, and by the time it was done … there wasn’t much left of the actual body.
“Plus they weren’t designed to do the job they were trying to do. Not something on this scale, anyway. So there were gaps. They built memories that were hardwired instead of flexible. They replicated a cardiopulmonary system, but it doesn’t work. And it doesn’t need to.”

Excerpt From Ex-Communication, pg 440-441
Peter Clines
https://books.apple.com/us/book/ex-communication/id635706546