Stop asking me to plan visits

My MIL and our family were NC for much of our daughter’s first year of life. Lots of things happened to where I needed a complete break from all communication with her. Her entitlement was just through the roof. Husband isn’t close with her, so it wasn’t a strife for him either. Since about a year ago, she’s been around and it’s fine. We visit occasionally (about once every 1.5/2 months). However, husband said he really wants it to be once every 4 months or so because it’s just really weird and awkward since they’re just not close and she expects 2-3 hour visits each time. Sometimes she’ll message him to ask for his plans and when will she see us again, and he blows her off. So then she will turn to me and blow my phone up asking the same things. I’m not about to pressure a grown man to see his mother every month when she’s craving the family time. So I just tell her I don’t know and then the cycle restarts. I know some women who like to be the ones making the plans, but for me, pregnant with our 2nd high risk pregnancy and being a full-time mom and homemaker, I just do not want to be the one who plans the social calendar. I have my own family and this lady raises my already high BP just by a text nowadays. How do I politely, yet firmly, set my boundary and let her know I’m not the one making plans to see husband’s side of the family? It’s really hard because she’s a lady you have to walk on eggshells around due to her emotional outbursts. My husband works 60 hours or so a week most times, so I can’t fault him for not responding to her, but just because he doesn’t respond doesn’t mean it’s time to blow up your daughter in law’s phone.