You're still around? Wow. I've been out all day and you're still at this. You know what? Word of free advice. Lie down. Just lie down, and imagine your girl fucking the other guy. Just contemplate it for a while. Imagine the screams, the cries, the moans. Their sweat mingled together. Her hair in disarray. His balls slapping her ass. Hell, maybe he's even railing her in the ass. Nipples hard, mouth agape, tongue running over her lips. Just ponder that for a bit.
Then, when you can't take it anymore, go run a bath, grab the toaster, plug it in, have a seat, and drop the thing in with you. Just see what happens, right? This is a win for everyone. It solves your problem (you), it solves her problem (you), and it solves our problem (also you).