L.F.
It's perfectly fine and normal to give her formula if she goes off food awhile. Some babies don't take to solids until a year or older. She could be teething, or changes around her could be throwing her off. A few times mine was teething, once he had a virus, and when we travel or change his schedule he doesn't eat as much solids. I give him formula or milk with a dropper of vita-sol if he's being finicky. He's a year old now. If he doesn't have other "sick" signs (fever, tiredness, congestion) I wouldn't worry.