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As far as going to the shore is concerned, I think that as long as you feel comfortable with going, it’s okay to go. She invited you by saying you should hang out with them so it sounds like she’d be okay with you coming. This gives you a chance to get to know some of her friends a little better too, and you’d get to have fun with your girlfriend. It sounds like it could be a win-win.

I understand you worrying about her cheating. I don’t think it’s something you necessarily can prevent, because if someone wants to cheat they will. I’m not saying she IS going to cheat, though. If she does cheat you’ll have to make the decision if this is something you’d want to put up with. It’s a huge violation of trust and it’s understandable if that’s something you can’t move past. Drinking or not, cheating is still a big thing and it’s valid if you’d be reevaluating the relationship if it happened. Honestly if it happens it may be a good idea to move on. You still have time to find someone in your life who won’t treat you like that. Of course, the ideal is that she doesn’t cheat at all.

I’d talk to her about the Snapchat thing. You can say that you noticed her snap score going up but that she never initiates it with you. Ask her if she’s upset with you. Make sure to use “I statements.” For example, “I feel ignored when I see that you’re sending snaps to other people and not me. I’m worried that you’re upset with me.” She can then explain what’s going on and hopefully you’ll be able to find a solution.