Why is my best friend angry with me whenever we hang out with a group of people
We're both 19. Basically I've been dating a guy for a few months who is very personable. Almost anytime we go anywhere, we invite people along. Of course, I always invite her. She can be excited to go, but when we get there she acts completely miserable despite everyone trying to cheer her up. For example, we were all in an arcade, and she just up and left and walked out to the car without telling anyone. EVERY TIME this happens. She's normally a happy person. She did this again the day I found out my great grandpa passed (a few days ago). It hit me hard, I was close to him, so I decided to just get out somewhere with a few people. She pulled this stunt, so I was trying to make her feel better while trying to hold back my personal hurt. She is a great friend and has helped me through so much, so it's not like she's a bad friend and isn't worth keeping around.
It's not that she's left out, if I love anything about my boyfriend it's that he is so personable and makes sure everyone's included, as do I. She just deliberately excludes herself from anything. Why go along every time just to act that way? She will be perfectly fine, even happy on the trip there, but when we get there she gets like that. After confronting her about it, she claims she was tired. This isn't true, tired is one thing, but to become a completely different person and exclude yourself from everything is another. Why does she act like this?