L.B.
It might just be a phase, but I think it a good idea to see the pediatrician in case there is something wrong with no visual symptoms. Have the sitter not make an issue of the problem, and maybe just set out small favorite healthy snacks and drink within the child's reach, so that she can help herself if she is hungry or thirsty. Perhaps food can be incorporated into a fun little learning game - is this salty, crunchy, soft, hard, etc.....