The daughter is 100% in the wrong on this one.

There has to be an unknown story behind this - something that has not been revealed to the public. The daughter must be harboring a lot of resentment for her father if she is favoring the feelings of her in-laws-to-be over the man who helped to raise her. There has to be a reason why she cannot get it together to tell her fiancé's parents that they either need to deal with the reality of her family or just absent themselves from her and her spouse's lives.