Was this rude of me to do?

i was at a friends bday party at her home. at the party she had this like blow up bouncy thing with an obstacle course inside. it was time to sing happy bday to the girl and some of my friends and i were just sitting in the little bouncy house thing. i said to my friends "we should go and join everyone" because they were doing the cake but they were like "no just stay with us". i listened to them and i know it was really mean of me. so now i heard rumors people were saying it was "bitchy" of me to not sing happy bday to her. they also said it was rude of me to get a piece of cake after not singing. i feel bad i should have went to sing happy bday.after i left the party i gave her a gift, said happy bday and thanked her. was this really terrible of me? i know it was rude, but please no mean comments