Should I tell her?

I want to tell her because she is a good person and I honestly like her a lot. I don't think what he did was right and me telling him "I think I should tell her" and him saying "Please don't. I want this to work" is not good enough. I am mad that he is juggling two people's emotions and he fucked up majorly.

On the other hand, I could understand that maybe I'm upset and my residual feelings are getting in the way of making a logical decision. Maybe I should tell her, but not right now?

I'm hurt not only because of the feelings, but because I honestly thought highly of him and thought he would be the one "ex" I could talk nicely about. I guess not though...

Kind of sad and feel weird about this...

So ex-Hopeful (someone I dated but we never made official) is dating someone else and that person is a friend of mine (we're not very close). He moved back to his hometown (which happens to be where most of my extended family is from). I'm not against him dating or anything, but 1) it's awkward that this is a person I know and 2) he has been carrying on with me over the phone with sexual text messages and I don't think that's right. If he had started dating someone he should have told me "Listen, I've started to date someone here and I think we should keep the texting to a friend level only."

Ugh. This does not make me think highly of him...I guess the person I thought I could have a good friendship with is not who I really thought he was.