50-50 faults tend to fuck both parties

if you are certain then talk to her tomorrow in the cold light of day about what you want to do, if it's a shitter shes driving and you know it's going to be 50-50 then just get it painted

whatever you do though DO tell your insurance company that someone hit you and that the conversation you've had with the third party has resluted in you both agreeing to not bother to claim as even though she's admitted liability as she hit you, the cost to both parties would be more than the hassle it's worth

don't mention any money changing hands as they may then use that against you if you then decide that it does need to go through the insurance

but call her, get her details, make sure you note the time of the call, who you spoke to, everything and then the same when you call the insurance company to explain the situation because you know that 4 years down the line someone is going to try and fuck you for it