Have I been rude to my GF's sis & has anyone else been embarred by their shoe size?

I hate to say this Nathan but you have really small feet for a guy and just because your sister's friend was paying attention to them it doesn't mean she was being rude, she was just having a laugh so you need to get a sense of humour. Telling your girlfriend's sister that her feet were huge and ugly was not only spiteful but it was also childish.