Its a sad situation and I dont honestly know what to do. I am not sure anyone would know what to do here. I feel like a bad person for kissing her but it made my heart feel so good. I think I am truly in trouble.
I think most would know what to do, even you but you cling to hope due to your codependency. She is a manipulator and a liar and if you allow it she will be a physical as well as an emotional cheater.
Don't believe her words. Tell her you need to see that she still loves and wants to be with you by her actions. Those would be her telling the other guy to leave, seeking councelling for her many issues and agreeing to couples counceling so that the same shit doesn't repeat itself a month or two down the road. All the same issues are still there in both of you that were there when you broke up.
It takes more than just love for a relationship to be a happy, healthy, functional one.
As usual, even thoug I'm blunt, I wish you well and the ability to see.
“The willingness to accept responsibility for one’s own life is the source from which self-respect springs.” ~Joan Didion