A. Your question raises a few issues.
First, how much juice does she get during the day? The AAP recommends that you limit younger children to just 4-6 ounces of pasteurized 100% fruit juice each day. If she is only getting juice during the day, then she is probably getting too much.
Next, she probably isn't getting enough milk if she is just drinking it one time a day. A toddler needs two to three servings of milk and dairy products or other foods that are high in calcium each day. Of course, if she is also eating a lot of cheese, yogurt, or other calcium fortified foods, then you may be fine with just one bottle of milk.
Switching to Whole MilkAs far as switching from formula to milk, there are several ways to do it. Many parents just take a 'cold turkey' approach and simply change all of their cups or bottles to whole milk once their infant is twelve months old. This often works if you have an easy going baby that adapts well to change. Only giving juice in a cup, and not in a bottle, can make this easier to do.
If you have a baby that is more stubborn or resistent to change, than a more gradual approach usually works better. Using this method you might just substitute one bottle of formula for whole milk every few days or weeks, choosing a middle of the day bottle which your baby will be the least likely to miss. The first bottle in the morning and the last bottle of the day are usually the hardest bottles to give up and the ones you should leave until she is drinking milk well throughout the day.
If even this method is too drastic, you might start mixing your infant's formula and the milk together. At first, just add a little milk, so that it is mostly formula still. And then every few days begin to put more and more milk in the bottles so that she gets used to the taste, with the eventual goal of just having milk in the bottles and no formula at all.
The fact that whole milk is usually cold might also cause a problem for some children. While you might be tempted to warm an infant's whole milk or let it come to room temperature, you might end up just creating a habit that will be inconvenient to keep up with. There is no rule that whole milk has to be served cold though.
In your case, since even this isn't working, you might try to get her used to drinking milk at some other time during the day and then work on her nighttime bottle. Or switch her from a bottle to a cup with the soy formula and then worry about switching to whole milk. Or you could keep her on a toddler formula until she is two and try to switch her to soy milk.
Since your toddler is still on soy, you should also discuss with your Pediatrician the possiblilty that she doesn't want 'regular' milk because of a milk protein allergy or a lactose intolerance.
And at some point if you make the switch and she just refuses to drink milk for a while, just substitute other sources of calcium into her diet, like cheese, yogurt, and other calcium fortified foods. And try not to force or push her to drink milk, as if it turns into a power struggle, she will likely refuse even more strongly and be even more resistent to drinking milk.
Bottles or CupsAnother issue when weaning from formula to milk is what to do with a baby's bottles. Do you switch to sippie cups too when you change over to whole milk at a year or give the milk in a bottle?
Again, it likely depends on your child. If you have a child with an easy going temperament who adapts well to change, you might try to make both changes at once. If you think that will be too hard on your child, then change to milk first and then get rid of the bottles later.
Best Milk for ToddlersFor toddlers without food allergies and who aren't overly picky eaters, they can begin drinking whole cow's milk once they are twelve months old. Keep in mind that the American Academy of Pediatrics recommends that you not give your toddler low fat milk until they are two years old.
A toddler formula is a good alternative if your toddler isn't able to drink whole milk, since they are available in soy formulations, such as Isomil 2 and Enfamil Next Step Soy. Since they are iron fortified, they may also be a good choice if your toddler is a very picky eater.
Although not recommended for infants as a substitute for an iron fortified infant formula, you could also give your toddler pasteurized goat's milk if you wanted to. Talk to your Pediatrician first if your toddler has a milk or soy allergy though.