According to the American Dietetic Association, children between 12-24 months need the equivalent of 2 cups (16 oz) milk per day for the necessary calcium, this provoides about 600 mg of calcium per day. Yes, whole milk is recommended to give the extra fat and calories needed for growth, but if she will only drink 2% milk, you can get the fat in other ways (whole milk cheese- see below). 1 cup of whole milk has 8 grams of fat and 1 cup of 2% milk has 5 grams of fat- not a huge difference.
Here is the fat and calcium content of different foods:
8 oz whole milk- 8 g fat, 300 mg calcium
8 oz 2% milk- 5 g fat, 300 mg calcium
2 oz American cheese- 17.8 g fat, 300 mg calcium
1 1/2 oz cheddar cheese- 14.1 g fat, 300 mg calcium
1 oz whole milk mozzarella cheese- 6 g fat, 143 mg calcium
1/2 cup ice cream- 11 g fat, 128 mg calcium
6 oz low fat fruit flavored yogurt- 2 g fat, 258 mg calcium
Hope this helps!