I've been away for a month, but I want to meet up with my friends without my girlfriend when I return.
Is it normal for you to do stuff without her?
Yes, and I miss my friends and I will tell her in advance.
So long as your honest with your girlfriend, it's good to spend time with your friends. Just make sure you spend time with her too and find a balance that works for your relationship.
Yeah I know.
I don't see anything wrong with spending time with your friends without your girlfriend as couples need to have lives independent of their partners. It seems like your girlfriend will understand and will enjoy spending time with you one on one.