your gf is lying to you. her lies become more and more obvious with every word that comes out of her mouth. she ignored your calls because either (1) she was literally ****ing someone else or (2) she realized she sent you the message by mistake and was avoiding you on purpose until she could think of a good excuse (although she sounds stupid and hasn't come up with one good excuse yet). she is a waste of your time, and i wouldn't be surprised if she is a hooker. this "gay" guy is not gay. she's sleeping with him. i would cut all contact with her and leave it at that. although, you are most likely going to have to deal with her if she moves back in a couple of weeks. is she going to live really close to you, or still relatively far?
in my opinion, even if she isn't lying to you (which is 99.9% not the case), she still isn't worth your time. the way she handled this entire situation shows how selfish she is, her lack of interest in your feelings, and how incapable she is of respecting you. dump her either way and don't look back.