What do you think about me leaving my girlfriend alone in my apartment while I have a drink or two with some friends?
Do you think that's really the right thing to do?
Actually I'm not sure if it's the right thing to do or not.
I understand how you don't want to always spend time with your significant other, but you live in your girlfriend alone while you have fun with your friends may hurt her feelings and maybe really bored in the house alone by herself. Why don't you go ahead and ask her if she wanted to join you and your friends, so that she doesn't get worried but also not get bored alone?
I'm going to do it anyways and apologize later.
If your partner can't come with you then you should consider just staying with her, I think she'll be happier spending time with you even if she doesn't say it. Sometimes ditching your partner can be horrible for your relationship, so make sure she's okay with it first.