My ex-girfriend is lying about me and I want to get back at her?

[Doug R]

Your first mistake was to buy ANYONE else a car. Even with a family member, it can, in most cases, be a bad idea. So hopefully you learn from that.
Sounds to me like you learned what she's truly like. You dodged a bullet there & should be glad you found out about her BEFORE you became even MORE fully involved. YOU need to see this & get past the emotional junk. Chalk it up to experience.
IF ANY of your " friends " say anything,....just shrug it off and say something like , " She's pissed that I took back the car & I'm lucky to get away from her & her lying & cheating " That's all and just don't go beyond that. Don't respond ANY other way. The more she posts on facebook and so on only makes HER look bad.
I would, however, make copies of any slanderous posts that may be needed in case you need to take her to court in the future. DON'T do anything foolish or down right stupid. Move-on and use it as a learning experience.