I hate to say it but it's likely just her age.. so not an awful lot you cando, but deal withit as best you can.
Pie went through a bit of a biting stage a couple of months ago, and it's become a big problem at her daycare lately. It can be due to teething, overstimulation, frustration - that seemed to be when we copped it; all kinds of things. We dealt with it by telling her firmy 'no' and removing her from whatever situation had caused it.

Good luck