Something that;s never made sense to me

In the first half of the movie, Tina's older friend Laurie accompanies her to a clinic for a pregnancy test, or checkup, something like that and Laurie has her young daughter with her. While they are in the waiting room, Laurie lays her child on the floor to change her dirty diaper and Tina asks "What does she eat?" Laurie says "Mostly applesauce, pureed vegatables, breastmilk at night..." Now I'm an only child and I'm just now pregnant with my first child, so I don't have much in the way of experience with babies and young children, but isn't a child that age a little OLD for that kind of primary diet? I mean the kid is obviously close to three years old and her age is even mentioned by Laurie's mom during the movie ("If she hadn't had the baby she wouldn't be bound to taking care of a three year old today" or something along that line.) She might have even been two, but she obviously wasn't an infant and was big enough to be running around. Shouldn't she have been completely on solids by that point? I might understand some soft foods like applesauce still, but BREASTMILK? It seems to me she should be LONG off of that. Plus, why is she still in diapers? I'm not really familiar with normal toilet training ages, but I would think that, at the very least, a child that age would have graduated to underpants during the day and a pull up at night. Like I said, it's not territory I'm very familiar with, as of yet, LOL, but I just found it a little odd that a child that big would still be basically on baby food and wearing diapers.