How should I tell this bitch of a woman off?

Everything in this thread points to you liking the girl too. If you don't already know this, you should be real with yourself and go from there. If you didn't care, this wouldn't be an issue at all. And, you wouldn't be attacking that other guy so much.

Jam it back in, in the dark.

And Hachifusa, people are going to hate you and their going to do it for very stupid reasons at that. You’re no mature than the other guy if you actually give a fuck about what he thinks. Now, I understand the spreading rumors part, but unless it was along the lines of you having a 2 inch dick or something, that’s nothing to get irate over.

The only way you’d get riled up over this shit is:

1. You’re immature and inexperienced.
2. You still like the chick. (this doesn’t have to be conscious)

If the guy is that big of douche bag then, when you talk to his girl, you should act like their relationship means nothing to you and blatantly (but playfully) hit on her/use lots of sexual references with her. She’ll probably go along with it, and he’ll get pissed off to no end. So much so that they might even break it off if it becomes way too huge of an issue with their (seemingly weak) relationship. If you do something like talk shit about him, or try and get revenge, then you’re nothing more than jealous asshole-loser to basically everybody.

There's nowhere I can't reach.

For the record, I don't think you're a idiot, it's just that you need to get used to this type of shit because somewhere along the line it's probably going to get worst. People that you thought were your friends will backstab you, a lot. Whether they are trying to or not.

Also, you didn't just mention the boyfriend, you made it a point to paint a picture of how much of a creep he was. It'd be different if the context of your post was something like "she's one of those girls that kinda axes friends when she's with someone" but your post was more like "her boyfriend is a creepy dumb pedophile loser creep^2." Jealousy, flat out.

Best advice summed up: Move on. People come and go in life.

This thing is sticky, and I don't like it. I don't appreciate it.