Hate to say this, but both parties need to chill and let things be. Your family may never accept her. And she may never feel "respected" by your family. They need to put on their big girl panties and act like adults.
They can act civil toward one another w/o fighting or getting nasty. Someone has to rise above it and say "I don't need X's respect here, but I can tolerate their presence for the sake of the person I love."
You just can't force these things. But, someone has to be the bigger person here.