s/w,
what an interesting and concise read
SpringD,
I recalled this morning that when J was really little, I borrowed and read parts of Dr Sear's Baby Book. There's a chapter in there on fussy eaters. Borrow the book and read it if that method suits you. Generally, it just says that some kids are too active to slow down for meals and their method is to cut up bite sized portions of various foods from different food groups, put it in a designated corner and the child will pit stop for food whenever he feels like it.
I obviously don't subscribe to this, preferring the "school's method" of fixed schedules. But I'm just highlighting an alternative from probably the other end of the spectrum. Also, since you're not the primary caregiver, it might be good to bring it up with her because doing both methods (confining to highchair or fixed meals) and this might just confuse your child even more!
My mom was a FTWM when I was young. During lunch, my grandma allowed me to cycle/run around the living and dining room and "refuel" after each round. But when my mom was home during dinner, she'd tie my legs to the highchair (using cotton strips...she says there was no seat belt then), and I would be forced to sit and finish my food. I could on that chair for up to 2 hours (crying, whining, etc but no much since I get whacked for that) but my mom and the rest of the family would leave me at the dining room alone when they finish and get on with their business. At 2 hours, my mom would get me and throw away what's left. She was tired too and told me she went to bed (around 9pm) soon after we did (8:30pm) during those days. All I can say for sure is that it didn't spoil my love for food...just an aversion to porridge for 16 years.
And after a while, I just ate faster since it was really a waste of time and really boring to be sitting there alone (no tv, no books, no toys, nothing)...I talked to my food (imaginative play!).