Urgent Help and Advice for Long-Distance Relationship

I’m in a long-distance relationship with my girlfriend who moved to LA for a job in aerospace engineering just a couple of months after we started dating. We've been together for two years now. I visit her whenever I can, and she tries to come see me too; we make an effort to connect when possible. We’ve discussed the idea of me moving out there with her, but I don’t bring it up often unless she does. I just turned 30, and she’s 24. During my last visit, I noticed the vibe felt off, and I saw scratches on her back and butt, which I've noticed before. This has led me to wonder if she might be cheating. Recently, she’s also been more rude and disrespectful towards me, and her roommate has made it clear that I can't stay for more than five days. It all makes me feel like the energy between us has shifted, and I’m starting to think I might just be a casual fling at this point. I'm at a crossroads: should I distance myself, break up, or stay in this situation? I genuinely want to move closer to her, and she has hinted that she wants that too, but I question whether she really means it. Do you think she’s been in LA for two years without becoming involved with someone else?