Why did I let this piss me off?

My "gf" was sayin hw she's going to go lay in bed with her friend & watch movies & I got pissed off even though her friend is 100% straight. I said it upset me that age told me and she went on "blahh blahh...lemme guess u'll be mad while were holding hands & if I give her a piggy back ride..etc at the movies" etc like wtf why did she even have to go overboard & say all the extra stuff. Some stuff came up & I couldn't go with her to the movies so her grieve is filling my spot. Her friend has a bf & Is 100% straight, or so she claims to be. Am I wrong for getting jealous? Am I wrong for feeling like she purposely said extra stuff to anger me.?