It seems to me that if she’s always lying to you about things, especially the types of things you’ve mentioned — meeting up with her ex (the guy she was obsessed with) and hanging out with him, making plans to go to parties that you’re not going to etc, — that you should consider looking for someone else.
Find someone who wants to go to parties WITH YOU and who wants to hang out WITH YOU and who doesn’t do things she has to lie about TO YOU.
You deserve better.