WIBTA if I told the girl my ex cheated on me with about me? 

So I was with a guy for about 6 months, and it was going really great. We had a lot in common and similar goals and we saw each other every weekend and just generally things seemed to be going well. Unfortunately he said he lost feelings towards the end and was trying to find a good time to break up with me. He didn’t want it to do it before I went on spring break and then he wanted me to see his new house. So when I got back from spring break he had me over to his new house. Everything seemed fine we hung out and just did whatever, I stayed the night and we slept together. The next morning I woke up to a text from a phone under a pillow. It said good morning baby. My heart kind of sank and I went through his phone and found a lot of texts between him and a girl he was hiding under a coworkers name. 
Once I saw enough to make sure I wasn’t seeing the wrong thing I woke him up. I told him I knew and I left. He saw me later that night so we could talk it about and have a real break up. He told me he didn’t want to hurt me and was planning on breaking up with me the next time I saw him, and that he never intended it to go this way. He lost feelings and met someone else, and from the texts I read it seemed like it had been going on awhile but he wouldn’t tell me how long. I’m guess around 3-4 weeks. I didn’t know who the girl was and then she popped up on my Twitter feed and not realizing who she was I followed her. That resulted in an immediate phone call about me poking around and I explain I wasn’t. We talked on the phone for two hours and I told him I knew I would get over this but right now we can be friends, and we again texted after and I told him I really can’t talk to him at all. He did kind of mention this girl was a “side piece” but I think he might’ve just told me that to help calm me down.  
This morning I woke up and the girl had blocked me. I can only imagine he told her to and that I’m some crazy ex and just to block me. But the thing is if I was in her position I’d want to know, and I don’t want him back. Sure we had a great relationship when we did but he did have a lot of things I didn’t love about him and I could never be with someone who cheated on me.
I mean he didn’t break up with me the night he saw me and then he initiated sex. And the night when we had our break up we still kissed and hugged for a long time. So WIBTA if I tell her? Part of me says I would want to know if I was in her and place and part of me says bud out and just leave it alone.  