I set up my girlfriend to see if she would cheat on me?

I dont find it wrong what you did. You obviously had a gut feeling so you needed to test her. So you did and the fact that she went along with it tells you everything about her. SHES A CHEATER. Like someone else said on here if she had the balls to sext with your FRIEND who knows what she might be doing with people you may not know or just anyone else whos not telling you anything. If you confront her she more than likely WILL get mad that you tested her but whos at fault here? Yes you tested her because you didnt trust her but was your instinct of NOT trusting her true? She failed the test so you had a good reason to do it. If she was a good gf she wouldnt have gone along with that. Talk to her and if i were you id just leave her.