Has she been to the vet yet? What do you mean by her acting strange? Concerning the food, sometimes you have to try different brands before you will find one that they like. I found two brands that Boots likes. I purchase the two kinds at the same time and alternate them at feeding times in order to give him some variety as far as food.
Also, what kind of food are you feeding her? I feed my cat only dry food and water. No people food either. I might, on occasion, but not frequently, give him moist food. My Boots is fifteen and most people can't believe he is that old. He acts and looks to be much younger.