What would you do? sorry long

my dad and his wife are in the middle of mediation heading for divorce in the near future. all four of her kids are in my wedding. her daughter is my BM, and her sons will be seating guests in the ceremony. she watched me grow up but she and i have never had the kind of relationship where you call each other and hang out a lot, and since i found out they are divorcing, and seeing what this is doing to my dad, i really haven't even shown my face at their house. i have enough going on, without their drama added. i try to spend more alone time w/ my dad now than ever, he's an emotional wreck, and i want to be there for him. but now this lady is causing DRAMA. she's talking to my sisters behind my back (who are still close w/ her) and saying 'I'm uninvited to the wedding' and 'i guess my kids aren't going to be in the wedding' ***???? where is this coming from? i've never said a word to her about it, and all i said to my dad was : 'do you think the kids will still be in the wedding? i WANT them to be.' and i haven't said another word.
my FIL's just stopped me from going over there after my mom called me and told me about this (she found out from my sister). but i REALLY don't know what to do other than talk to my dad, and have him handle this. i can't stomache her right now. and it also irks me that my mom has to get involved, why she cares, who knows! i'm ready ro shut off my phones and hide in my bead!
what do i do here? i don't care if she comes to my wedding, its really up to my dad. and i WANT her kids in it still. i love them and they have nothing to do w/ the divorce! help!

If you want the kids to help out, then keep them in the wedding. If she keeps being snotty, then you don't have to invite her. You've got time, so give your dad support now. Don't start in on whether you should invite them to the wedding. That should be last on his mind right now.

Since you have time, I think you should give it a month or so and see how your dad is doing. Be his support right now. Then when he's doing better you can ask him what he thinks. Good luck!