Hi there -
Bless your heart...I know how hard it can be to break a child from the bottle. I have two young children, and when both of them were one, my mother (who was taking care of them while I was at work) insisted that we introduce them to sippie cups. I thought, "Great! This should be easy enough!" but it was harder than we thought. It took about a week of whining, crying, and sometimes screaming well into the night before my kids actually grew accustomed to the idea of drinking from a sippie cup. It should be noted that while we didn't have twin babies to worry about waking up, we had a house full of working adults, who were definitely not happy with the thought of being awoken by tyrades of tears. Talk about will power...we, as a family, just agreed that this goal had to happen and we stuck to it until it did. It was the same thing when we broke our children of their pacifier usage. Breaking the bottle doesn't have to be all about tears and anger...part of the trick to it is to figure out which cartoon character your child likes best, and buy that sippie cup. Make it a big deal, and don't show any signs of fatigue or frustration with your child, or she will pick up on it and do the contrary thing you want her to do - they're so smart!
Above all, it's about WILL POWER, which you can draw upon by keeping your child's best interests at heart. Trust me, I grew up in the Philippines where children were left on the bottle way into their fifth year of life! As a result, they had rotten teeth, which fell out way before they should have. Also, those kids who went to sleep drinking the bottle had vicious ear infections because they were lying down and drinking. Sippie cups are definitely healthier at your daughter's age, and easier to work with especially if you're potty training her now.
Good luck!