Hi H.,
My daughter just turned one and I'm doing the soymilk/cup transition as well. This morning, rather than warming a bottle for her, and then giving her breakfast. I actually poured cold soymilk in a sippy cup (holds 6 oz) and she drank it together with her breakfast. For lunch I will do the same thing. When it will be tricky are the two bottles that I give her (warm up) before her afternoon nap and bedtime....As with my son (who is now 4), I will take it one step at a time. I think for now, transitioning 2 bottles to a cup is fine. Once we get that down pat, I will then work on the nap bottle and then finally the bedtime bottle. Just remember, baby steps!
Also, her pediatrician said she should be taking about 24 oz. What's good about milk vs. formula is that it doesn't go bad after 1 hour. So, I put her cup back in the fridge and as she's playing I give her the cup - she usually finishes the cup, it's just not in one sitting as with the bottle.
Calcium is important - I will begin supplementing with a multi-vitamin and calcium (as I do with my son) now that she's getting off of formula.
Good luck!! Feel free to email me with questions or to chat: ____@____.com.
~J.