If I was the "other" woman, Should I tell her he's a cheater?

I was seeing/dating a guy casually for the past two years....and then recently ended the situation and confirmed that he is with another woman. I am not jealous or vindictive, I truly do not want her to be in a situation like I was! With us it was more casual, but I knew he was up to something. After a while, I didn't want a part of it anymore, since I want a real man. Going under that train of thought, if it was my man, I would want to know! I do not know her at all, but I have her contact information. Should I tell her he's a cheater? What is the best way to approach it? I have plenty of proof of his indiscretions, and he swore up and down the entire time he was "single."