Is it ok to miss my ex who cheated on me?

I was cheated on from the very beginning of my relationship with her. She was seeing her relative, and he didn't know she was in a relationship with me. They went on dates during our first year, and in our second year, they became physical. We broke up in our third year , and she started dating another guy from my college while still dating her relative . While I was grieving our breakup, I repeatedly asked her if she is dating the person from our colg, but she denied it many times, even though she also became physical with him. In our fourth year we patched up, I discovered the truth about her dating him, and I tried to accept it, but then I got know that she’s been cheating on me from the starting . Now, she says she is sorry for the mistakes she made and wants me back in her life.