I (33F) have been with my boyfriend (33M) for over 6 years and we own a house together. His family lives about 4 hours away by car. Later this year, his sister is getting married. She has 5 bridesmaids but sadly, one of her bridesmaids and best friends has been diagnosed with breast cancer. She doesn’t know yet whether she will be able to carry on her bridesmaids duties for my boyfriend’s sister. As a result of this, last Thursday, my boyfriend’s sister called him and asked him to ask me, if I could be a stand-in bridesmaid for her big day. She all but said “I couldn’t think of anyone else to ask so I’m asking you”. She and I get along well but are not close by any means. To be honest, I don’t really want to do this for her. My opinion of her is that she is a bit demanding, spoilt, rude and overall doesn’t treat my boyfriend the way he should be treated despite everything he does for her (she says jump, he says off what bridge). I am still considering whether I want to do this for her or not. For the sake of my relationship I’m torn between doing it to keep the peace, or standing my ground and making my position known to her (I won’t jump if you ask me to). At the same time I feel so deeply sad for her friend who is sick. I think she would feel much better about not being able to continue as bridesmaid if she knew there was someone else there who could stand in. WIBTA if I said no to this request out of principle?