is this wierd? must read to understand! :-)?

My birthday party is on the same day as my moms friends daughters birthday party. I am going to her b-day after mine. I invited my cousin, but she lives really far away (she is coming) so she was going to spend the night. BUT then I would have to bring her to the other girls b-day party. my mom asked the other girl thats having the partys mom and she said that would be great. my mom is perfectly fine with it but my stepdad thinks its really rude and a bad idea. what do u think is the better thing to do? sorry, this question is REALLY confusing and long but I REALLY appreciate it! THANKS!!!! :-)