Short background: I moved to a new city a few months ago and almost instantly started dating this girl. We've had a lot of ups and downs in the relationship, and it perpetually keeps me a little on edge. When things are going well, they are going really well. Every couple of weeks though it seems there's some major blow-up where I reconsider dating her (usually stems from a situation when she drinks and it mixes with her medication poorly which leads her to just start getting angry with me). As we've kept dating though we worked through a lot of our issues and I'm finally beginning to believe that we're moving in the right direction.

So a couple of weeks ago another friend of mine (who also lives in the city) asked if I wanted to go out of town with a bunch of her friends during Labor Day (they're hosting a 100 person event). Thinking that it would be great to meet new people (I only know 3 in town) but not sure if I wanted to spend the money, I pondered it over for a couple of weeks. This weekend I was forced to make a decision by Sunday at midnight. I mentioned it to my GF a few hours beforehand to which she responded "thanks for the invite" (obvious sarcasm) and then a little later said "oh, you should go. It sounds like a great way to meet people" (I missed the sarcasm here). Anyway, I decided to go and she was pissed. We still had sex that night and in the morning things seemed better. For that reason, I thought she was okay with making separate plans.

Last night we grabbed drinks (mistake) before dinner and she started getting angry about it all over again. I was drunker than her and kept saying I wanted to discuss it sober because this wasn't healthy. This kept going for awhile until she just said "fine, I'll put you to bed because I take care of people". I passed out shortly after that.

This morning I don't know what to do. It's like I want to invite her to make her feel better but this is something I'd also much rather do alone. The reason for the latter is that I can't yet feel comfortable when we're meeting new people together (especially since there will be drinking). In the past, she's been upset whenever she doesn't think I'm talking enough to her in large social groups and this fuels her anger at a later time.

I have very little experience dating someone more than a few weeks, so maybe I'm also failing to grasp the concept of how big Labor Day weekend is to a relationship. Since we are making progress and I'm starting to realize that she's a true bright spot in my life, is there a good way to handle this moving forward?

TL;DR My GF makes me uneasy when meeting hanging out with my friends and I'm taking an opportunity to make new friends on LDW by going solo. She's pissed at me and I don't know what to do.