She has probably lost a bit of weight if she's been sick - it's really surprising how much they can loose in a short time, but it's mostly fluid so she should gain it back pretty quickly if she is already back to eating normally. If there are no medical indicators of why she is still only that size, then it could just be the way she is meant to be. She does have a pretty good diet considering she's a toddler ROFL! But definitely bring it up with your Dr if you are still concerned by then.