Should I forgive my cousin?

Me, my cousin and her friend went out Saturday nigth to a cabaret. My friend, who is her s*x partna and married showed up with his friend (male) like 10 mins lata. He sat next to her and me and her friend felt like that, this heffa knew he was commin and didn't tell us! Well, around 1am my friend and his friend left and me and her friend went to dance....my cousin left the table before we went to go dance. When he came back she was still gone. We went outside and called/text and no respond. Her friend kept sayin let me go n da back and look for her, but i told her NO! We gonna wait so i can curse her azz out!! She pulls up in front of her car with my friend (her s*x partner) and say she wasn't doing anything. We felt used and i think that was inconsiderate, credy and more. She begged me to go to! She should of did that on her OWN TIME!!