GF of a year told me yesterday she was going out with a guy and a girl (both HS friends) to take pictures. I said ok and she sent me what she was going to wear (it was normal clothes, long pants, t-shirt). She always keeps me updated and just now she told me she is going to the guy's car as he is driving them to the spot. I got pissed that she didn't tell me yesterday he was going to drive. She told me she didn't know, but still went in.

I still don't know why I am angry. Perhaps it's her letting power go (giving up control) by going into his car? I called her just now (she is still out with friends) that this does not work for me. She asked if I was angry multiple times. She told me it is never going to happen again. We exchanged back and forth with her defending herself that she didn't know, told me she was going into his car beforehand (right before) etc.

What should I do? I never behaved this irrational in front of her by letting my emotions take control. This was the first time that I let my emotions drive me. I told her we will talk tonight. I am planning to tell her that this behaviour is not allowed because you are giving up control. What do you think?