Her insurance is already on the hook for the property and hospital bills as it stands now as it was clearly her fault.
If you chose to sue, it would be for future long term problems from the accident which without a very precise diagnosis just ain't gonna happen (torn muscles, broken bones, organ damage, concussion, etc....)
Suing is just designed to "make yourself whole"
You wouldn't get shit for punitive damages against a 90 y/o woman.