I am afraid you already lost her. It seems she wants to have her cake and eat it too. I get the impression she likes both of you, and wants to play on both sides, or she is on her way to dump you eventually. She spends more time with him than with you, and that is not good. She finds the other guy funny, and that's usually a sign that she likes that aspect of him a lot.
To ask you if she can kiss him is tantamount to saying that she wants both of you. She wants to know how really jealous you are, so that she can manage to keep you in her relationship until she decides what to do. My advice would be just as some others here have said. Move on!
If you move on, she may realize then that her love for you is strong enough to keep a one-to-one relationship with you alone. But from experience, I can tell you she is not a keeper. Keep an eye to see how she manages phone calls in your presence, and if she is anxiously expecting a call. If you see any tendency there. Move on fast. You lost her heart!
I know this advice is painful to follow, but in the long run, it may be your best bet. I hope that helps.