that's tough. if she cheated with two guys and you were doing everything in your part to keep her happy, then maybe she just doesnt really care, and now that things didnt work with the other guys she wants you back.
or she could be truly sorry.
i wouldnt be able to tell you cause i dont know her, but do what feels right in your heart or whats gonna make you happy. forgive her maybe, but dont forget, and maybe give her a second chance, cause people deserve it if they truly want it enough. but make her WORK for that chance, and if you start going out again, be kinda "whatever" about the relationship, so if she does it again, you just look like you dont give a ****, and its her loss.