My girlfriend and I are going to a Christmas eve party tomorrow?

well I am a stud woman and quite big 5'7 almost 300 lbs . Well she rented me a Santa costume and her a Mrs. Claus outfit . Should I be Santa ?? I love her and want to make her happy but I don't know yet well she is going to be mad if I don't . Yes I am big and stud but still not sure what to do . Ty for help on this happy holidays to u all