Hi N.
Yes, like both responses said, it sounds like what she is eating is not agreeing with her. My children also all had allergies, and when the formula or breast milk wasn't agreeing with them, they always wanted to eat as well. Their little tummies hurt when digesting the food, so they think they want to eat again. You could try a different formula (soy), but if she's like my kids, it was dairy and soy allergies, so even that didn't work. Unfortunately, that's when you have to get into the more expensive formula's. The good news is they usually outgrow it before too long.