"Hey, T.C.!" I know this is a tricky situation, but trust me I've been there. I, too have a friend that I love like my family. He too went out with someone who had betrayed me.

Well, unlike Jeremy, Austin saw my side of the problem and trusted me as his friend to help him make the right decision. I had to gather up all my courage just to go over to him. I intended to tell him to break up with... well, for her sake we'll just call her Susie. After I had thought about what I was going to say (like, "Austin you HAVE to break up with her; do you know what she's doing to you !?!"), I realized I wasn't the one to make the decision, he was.

Instead, I walked up to him and said, "Austin, you know what Susie's done to me? She went and said (for my sake) this and that behind my back and it wasn't true. I don't want her to hurt you. I care about you and your feelings and as your friend, am trying to bring this problem to your attenion."

I'm advising you to calmly and lovingly tell Jeremy how you feel, your story of what she has done, and make sure it's clear that you don't want to hurt him.

Good Luck T.C.! By the way, I love your name!