<human>: Can you provide a brief overview of the text?

So I have been discussing with my girlfriend about seeing the new deadpool movie. We promised we will see it together and today she said she might be able to see me after her volunteering. However, after, her brother picked her up with her friend and her brother (who's 5 years older than her) met with his friends and they decided to go see deadpool. Is it okay for me to be upset or is it right that I do feel sad that she broke her promise and went with her brother, her friend, and her brother's friend who wanted to see deadpool?
<bot>: girlfriend said we would go see a movie together this week but ended up seeing it today with some other people. Do I have a right to be upset?