What I did when my kids needed to switch to milk was to mix the milk in with their formula. You need to use whole milk with a child who's under 2 to insure they still get enough fat.
Start by substituting 2 oz of milk in each bottle (so, 6 oz formula, 2 oz milk for an 8 oz bottle) for two weeks. The next two weeks, make the bottle half milk, half formula. Continue adding more milk every two weeks until you are no longer using formula.
When you add the milk, make sure it is a little cooler than the formula (if you feed warm bottles) so that a cold milk bottle won't be strange to your daughter. This method worked very well with my kids and was recommended by their doctor at the time.