Some "help" you just don't need... And perhaps one doesn't realize it until you meet the person. I would go with your instincts on this one.
I was in a similar situation with my MIL. Abrasive, self-serving, party-girl personality. Really only wanted for me to be in total awe of her mothering skills, such as "Watch me hold the baby". Not relaxing to be an audience at these tender times.
Her visits have basically been total nightmares as we struggled to keep her happy while taking care of the new baby (ie, attending to two babies). She expects to be shown a good time and is totally flabbergasted when I suggest helping (does the "helpless me" thing: I don't know how to use your washing machine, where are your pans/spatulas, even when shown asks repeatedly). With schedules thrown off b/c she wants to go to a new and different restaurant for EVERY meal, I was exhausted after the last visit. The visits end with her blowing up (yelling & tears).
This is not quality family time and is not good for the relationship (marriage and familial). What works for us is short visits and no visits. She lives 3,000 miles away, so short visits are hard- but if she is traveling anywhere within 3h of us, we'll drive there, stay in our own hotel and visit for a limited time (2-3h per day, subsequent days ok). This also works because then we are on neutral ground. She actually goes on Match.com and "dates" a couple of men in the meeting city (really bothers me that she'll use the pretense of a relationship to be chauffered around and get meals for free, but that's definetely in the "her life decisions category").
It is just not worth the stress and damage to the relationship(s) to let her visit on her terms. If I were reading this, I would think I was heartless, but until you are in the horrid situation, you might not understand it.
Best regards to all!