I think that Mom-in-laws mean well, but often forget the logistics of raising children, since most of the time it's been many years since they have!!!
I also have more strict eating rules during daycare hours, and my kids abide by those, during daycare hours. And since doing so; I have found them to be better eaters in general!! It has been a wonderful side effect, since they can be pretty picky.
I really, really believe that if kids are hungry, then they will eat. I read one time at our public health office "It's a parent's (or caregiver's!) job to decide WHEN the child eats and WHAT to serve. It is the child's job to decide IF they will eat, and HOW MUCH." I liked that.
PS> This mom really thinks that her child will absolutely starve if she doesn't offer that jarred junk food??? Yikes. Methinks there are bigger problems to come!!