Show and Tell?

Dear Suz-
I need help with a situation that I am in with my best friend and her boyfriend. It's definitely not a love triangle because he doesn't love her, and he doesn't love me, he's a player. But I got drunk one night and ended up going home from the bar with him. We had a great night and have continued to see each other off an on. I knew him and even slept with him a lot before he met her. The bad thing is I haven't stopped having sex with him even though she thinks they have a great relationship. Should I tell her what has been going on, so that she will give up this dream of the perfect relationship, or should I just stop seeing him and let her get played like every other girl who gets serious about him? The main thing is that I feel bad about having sex with a guy that my best friend thinks she is in love with.
~ Sneaking Around

Dear Sneaking Around,
I can imagine that the idea of having sex with your best friend's boyfriend is tearing you apart. But hey, good, no strings sex is hard to give up. At least you see him for the player he is. Your BFF obviously thinks he's a good guy.
I believe if I were you I would tell her. Heck I might even tell her in front of him by asking him if I left my thong at his place after the last booty call. She may be mad, but when you explain to her that you and he were seeing each other before she even met him and that you didn't want her to end up getting hurt by him she may calm down. Be sure to tell her that it probably wasn't just you that he was sneaking around with and surely she will see that she is better off without him, or at least better off knowing the rules. If she continues to see him that will be on her.
As for you, don't you think you deserve better than a guy who only uses you for sex? Why don't you dump him and look for a nice guy of your own, then you won't end up in this situation again.
Thats how I would handle this situation that isn't a love triangle because there is no love involved.