S.G.
Yes, start giving her whole milk a few times a day instead of formula. Put the milk in a sippy cup only, NOT in the bottles. Only formula goes in bottles. Even if she isn't taking the milk, still offer it instead of the formula. She knows how to drink out of a cup so she just needs to deal with the fact that she isn't getting the bottle as often. In a few days, offer milk a few times a day in the cup and drop out a bottle feeding. A few days later add more milk while dropping a bottle.
For most kids this age, the bottle is a habit not a need and if you just stop giving her the bottle she will get over the fact and move on to bigger and better things. If you must give her a bottle, put water in it. Don't make it worth her time to have.
Good luck and stay strong!
S.