I feel like my girlfriend of almost four years and I have been drifting apart recently. I work to pay our bills and she is in college. Recently, she has gained new friends, some of which are guys.
I found out that she has a crush on one of these guys (one that she doesn't really know that well so they don't hang out).
Two days ago, we had plans to finally have another date night after about three months of trying to find the time. She ended up making plans to hang out with a bunch of friends because she forgot about me. Turns out, all of her friends bailed and it was just her and a guy friend (not the one she has a crush on). He paid for dinner then they went to his dorm to do homework. After that, he brought her home and walked her to the door. I didn't know any of this was going on. I found out about it when she got home. I got angry because of the situation being a LOT like a date. Nothing happened between them, but it still stings.
She doesn't seem to understand why I'm upset and thinks that I don't want her having any guy friends. I don't know how to get her to understand that I don't mind her having guy friends. I just don't like the way our relationship is going because of her willingness to omit parts of the truth.
I'm not sure what I've done to turn our relationship in this direction. I love her and I don't want to lose her. What can I do?