What Should I Do If My Girlfriend Barely Talks to Me?

I'm having a really hard time with my girlfriend. She's barely talking to me at lunch and acts like I'm annoying. Her mood is all over the place, and I don't know what's wrong. We talked about how her mood swings might mean she's dealing with something bigger, like stress or not being into the relationship. I was told I should try talking to her directly about how inconsistent she's being. I realized I can't fix what's going on in her head and that I shouldn't have to walk on eggshells. I need to have a real conversation with her about how I'm feeling. I'm going to give it one more shot and tell her how I feel about her being mad at me. If she still brushes me off, I'll know where we stand.