she is pretty tiny. I would think no more than 6 weeks. It could be that the flavor of food you are giving her just doesn't appeal to her. You should try some kitten kibble. She should be feed kitten food for the first year of her life to help give her all the nutrients she needs to be a healthy cat and to boost her immune system to fight off any kitten diseases she may come in contact with. Has she been to the vet yet for a check-up? That is always best as they can give you an age on her and tell you when she needs her needles and all those things. They can also help you with choosing the right food for her.

I am sure you will get lots of advise from the experts here.