I'm placing this here, on behalf of a friend, because it really has more to do with family dynamics than a wedding.
B/G: I have a close friend that was born with her left arm truncating at the elbow. Her parents did not raise her to believe that she was disabled in anyway and she goes about her life in the same mindset. She is an outgoing, energetic and perfectly capable woman. She's only person I know that can change a baby one-handed!
In short, while she has a prosthesis, she very rarely uses it as the effect is purely cosmetic. Wearing the prosthesis the uncomfortable for her and actually limits her use of her left arm. She freely admits that she cannot remember why she got the thing in the first place.
My friend, Susan, has been asked to be a bridesmaid in her brothe Dave's upcoming wedding. Dave is marrying Louise. Louise and Susan are not particularly close but Susan has been subscribing to the theory that she loves her brother and while she and Louise do not have to be friends, they have to be respectful and civil.
Louise recently organized an outing to select bridemaids dresses. Susan was unable to attend due to a work commitment. Louise later emailed Susan picture of the dresses selected: a knee-length halter top for the other 3 bridemaids and a high-necked, long sleeved dress for Susan. Louise explained that she was trying to make Susan's prosthesis look as natural as possible.
Susan was pretty shocked by the comment and as tactfully as possible explained that she was not planning to wear the prosthesis and that she would prefer the halter top dress. Louise replied that Susan had to wear the prosthetic arm and the chosen dress, as the missing portion of Susan's arm makes Louise uncomfortable. Furthermore, if Susan refused, then Louise would like her to not only resign from the bridal party but not attend the wedding!
Susan has no problem dropping out of the bridal party (at this point she doesn't want to do it any way) but is at a loss to explain to her family why she won't be at the wedding. She doesn't want to cause a rift but she can't just refuse to attend without an explaination. Dave, for the record, doesn't want to be put in the middle.
To complicate matters further, both sides of the family live locally, so Susan can't use distance/time/money to get out of attending.