Shelter Cane not eating much

We got our sweet 3 year old girl Freya from a local shelter and day one (Friday) in the house she ate 2 cups of food. Since then, she hasn't ate much. She'll eat some bites, walk away, then come back, eat some bites, walk away. Does anyone have any advice to get her to eat some more? She's living an active lifestyle and we're worried about her losing more weight (she was 70 pounds when we got her). She also hasn't been drinking a lot of water.