I know how you feel I was in a similar situation and had to tell one of my bridesmaids to beat it, it’s not a nice thing to have to do no matter your feelings towards the person.

I called her and told her EXACATLY how I felt and that I no longer wanted her to be a part of our special day, and that judging by her comments and actions it was obvious she didn't want to be a part of mine. I felt sick to the stomach before doing it (even though she showed no respect for me), but was relieved and at peace once I had done it. I offered to buy her dress and shoes off of her so then she had nothing more to ***** about, as like you it was only a couple of weeks out.

Weddings are a day to celebrate the love and commitment of two people, you don’t want ANYONE there that doesn’t wish you well. Your MIL and SIL obviously have no qualms about disrespecting you (and your DF) so my advice would be to get them out of your life. Life is too short to have to deal with people like that.