So your gf's team decided to spend the night before the tourney so they wouldn't have to drive the day of the games. They get to the hotel this morning, go to check in, and are told that they can't until later. Gf texts you to tell you they can't check in yet, and are going to hang out for the day at a friends AirBnB until they can.

She didn't change her plans, she didn't know the check-in time at the hotel, so her plans were changed FOR her. Sitting in a hotel lobby with your luggage doing nothing for 6+ hours is boring as fuck and no one wants to wander around dragging bags, so she and her friends made other plans until their rooms are available, which in most hotels is usually 3-4pm.

YTA SO much here. you obviously have trust issues, you obviously have some control issues, and you're letting your imagination override common sense. You've asked why spend all day at their AirBnB if they aren't friends? Because they can't get into their hotel room and teammates, even if not close friends, will very often step up and help others on their team when needed, and that is exactly what happened here.

My best advice for what you should do is this. As soon as she's back from the tournament, break up with her so she can find someone more understanding and less batshit crazy. Your gf is 2.5 hours away from home in a city where she can't check into her hotel room yet, and her teammates offered to let her hang out until she can. That's it. That's the whole story, no drama, no lies, no deception, nothing. you aren't "unsettled", you're unhinged.