help a reader out: I can’t enforce my house rules- they’re following 'doctors’ orders'

Alright my wise and wonderful readers, help me answer this one! I'll weigh in soon, but love what you guys come up with, and other mothers are such an amazing source of wisdom...This was inspired by my recent post about failure-to-thrive, but also relates to a post about protecting your kids from difficult feeding situations. What about when it's in your own home??"I struggle with a related problem with one family that lives a couple hours away and frequently stays with us when they come to our town. Both their kids were extremely premature and had growth issues – the younger is 3.5 and has had a feeding tube since before she was 1. Their mother always pushes as much rich food as she can, all day long. (The little one is not permitted to drink water, ever. She drinks milk with extra cream added.) The older one has suddenly become quite plump, which I suspect is her normal shape (she looks a lot like both her parents), but her mother is still in the mindset of pushing her to eat.I’ve mentioned Ellyn Satter to the mother, but I don’t want to push an agenda on them, even if I suspect it would be better for their kids. My problem is that I can’t really enforce my house rules when they visit, given that they’re following doctors’ orders. But it seems unfair to my daughter to not be allowed to share in whatever snack her friends are eating when they visit, so she often ends up with lots of extra “treats” at odd times, throwing off her regular eating schedule. (Last time the visit also disrupted her sleep schedule...)Right now the visits are infrequent enough that I don’t worry about it too much, but it bugs me a bit, and it could certainly become more of an issue over time. I also don’t really know what to tell my daughter about the different rules. I don’t have a big problem telling my nieces to knock it off when they start rummaging around in my refrigerator 20 minutes before dinner, but this is different somehow."