If your baby is good at taking a bottle, just start feeding her a bottle that is 3/4 breastmilk, 1/4 formula. When she is willing to take that, slowly start increasing the amount of formula and reducing the amount of breastmilk.
Does she take bottles with breastmilk easily? As someone else mentioned, it might not be the formula at all, if she isn't accustomed to bottles. Don't give up on breastmilk, if you can. Keep trying to boost your supply! Good luck!
Updated
If your baby is good at taking a bottle, just start feeding her a bottle that is 3/4 breastmilk, 1/4 formula. When she is willing to take that, slowly start increasing the amount of formula and reducing the amount of breastmilk.
Does she take bottles with breastmilk easily? As someone else mentioned, it might not be the formula at all, if she isn't accustomed to bottles. Don't give up on breastmilk, if you can. Keep trying to boost your supply! Good luck!