
Good luck getting her to sign anything. She has the upper hand.
a. you hit her
b. she has an accident report to back that up
c. if you don't don't give her the money to fix it then all she has to do is call your insurance company and they cover it.
If it were me, I would tell you to stick your agreement. BTW, I'm not sure what you were implying when you said she was going to the gym. Were you saying she obviously wasn't hurt since she was working out, or that she was going to the gym to recover from an injury? Because maybe she's doing rehab at the gym.