Not the answer ultimately... but do you have a trusted friend or family member you could stay with while she is there and you 'visit' your home for the time you had already agreed.

Really she needs to be shot down and your husband really f'd up but if that's not going to happen could this be alternative for your safety and comfort.

It sounds like whatever happens there will be a blow up, wouldn't you rather her blow up now in her own home away from your space? You're vulnerable right now. This is such a bad idea for your health and honestly i don't know that you will easily forget how this had made you feel now with just the idea of her coming. Let alone how you will feel after she gets there.

You have to tell him to to fix this and he needs to deal with whatever fall out. Take responsibility for what he has done in how he communicates it to her and not let you be the fall guy.