There is a saying "Once a cheat, always a cheat". It wasn't 1 time, 2.5 years ago, it was countless times over 2.5 years.
You 2 get back together, your teaching her that "Hey, I can fuck around on this guy and he will stay with me."
Relationships need trust. She lied for 2.5 years. The most important thing for men in a relationship is loyalty.
Block her number, block her on facebook, delete any texts, remove all photos from computer.
Out of site out of mind. If she is inviting you over for dinner, she already regrets it.
If you feel the urge to see her to fuck, I suggest rubbing one out. It will help with the urges.