Yeah, so even if she IS banging another guy she's trying to drag you on behind her as a backup. It's called sending her a response that simple reads. "Stop contacting me."
And be done with it. You deserve better treatment than that, even if you love her. Stand up for yourself and respect yourself. Then maybe she will respect you as well.
"Well, then," the Cat went on, "you see a dog growls when it's angry, and wags its tail when it's pleased. Now I growl when I'm pleased, and wag my tail when I'm angry. Therefore I'm mad."