Would really love to know how to move past the cheating

For 6 months my partner and I lived a part. I thought we were still in a supportive monogamous relationship it's just that in that moment of time we were both committed elsewhere for work and living...I thought that we would both have no issues being faithful.

7 weeks later I receive an email off my partners email address telling me her name and that her and my partner were in love and that they were together and could I please leave them alone to get on with living life.

I quietly put the email away and shut that part of me down and continued on living life as if everything was ok no one suspected a thing because when people would ask about her I would reply she's good and doing well and then say nothing else.

At the end of the 6 months of living a part we ended up in the same city again and it took no time at all for her to reach out to me. We talked and decided that it was a mistake one that she regrets and that she was sorry and would never do it again. The out of it thing is is that I believe her I really believe that she learnt her lesson and that she wouldn't do that to me again however the other women keeps popping up in our lives, and it doesn't seem to matter how many times she is blocked on social media, via email text and phone calls this woman just keeps on reappearing like a bad penny.

I get really upset when this happens and we end up arguing terribly. I just can't help myself I feel like I'm back in the beginning when I received the email. I hate that period of time and would really love to know how to move past the cheating.

Any ideas would be appreciated