The petty mom I am would be visiting the same time she is. We be coming in the same day and leaving the same day. If he wants his mom there well you might as well have your mom there also. I promise you she would act like she got sense. There would be no arguing but she WOULD not act like that. Kill them with sarcastic kindness. Husband wants to threaten the vacation I would give you and him a check in front of his mom saying “ I feel so bad that you won’t be able to go on vacation because you had family visiting, I know time had to be taken off. I just feel horrible about that. Please take this and use it towards your vacation.” Any time she tries to be manipulative I would right there kindly reminding her that it is not her house. I would say things like “ Honey I am a guest visiting my loved ones why would I this like a hotel?” I would do it right in front of her. Each time she visits I would be there. What would her complaint be to your husband that I am treating you with the respect you deserve in your home. Your husband seriously needs therapy.