I am not a big "do things on a schedule" person. Our grandkids stayed on the bottle until they were ready. Most were off the bottle by 2 years old. One was off by 2 1/2, one day he brought me the bottle and asked for a tippy cup.
The reason why I am not a "be on schedule" person:
My daughter was about 13 months old and she fell off the couch onto her bottle and ended up knocking a tooth loose. She had to go off the bottle that day and was NOT ready. But the sucking would pull the tooth completely out and the doc wanted to give it a chance to stay in her mouth. So, she still needed to suck and guess what was avail. Her fingers. She sucked her fingers until she was nearly in Jr. High. Her jaw is recessed and her teeth so crooked they wouldn't even waste the time and effort to straighten them without breaking her jaw first.
To say the least, if one of my grandkids need to stay on the bottle longer I don't care. Bottles are easier to remove and fingers are there forever. I talked it over with our pediatric dentist and he said it's the holding the milk in their mouth for extended hours and hours is what causes tooth rot. And any substance can cause it. Saliva naturally cleans the mouth. If the bottle is carried around in the teeth all day or held in the mouth all night the milk/drink is never rinsed away. So the drink sits on the teeth for a long time and eats away. If she is drinking and then going on her merry way she should be fine.
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About the milk in the tippy cup. Try flavoring it with a tiny amount of choc. syrup or strawberry syrup. You can always use fresh fruit instead. We had "purple cows" at my child care center often. It's blueberries and milk mixed in a blender. Sometimes I would put a bit of ice cream in it too and the kids would drink it up.
Did you make the move to milk gradually? I always transitioned the baby room kids by mixing 2 oz. milk with 6 oz. milk for about a week, or until they took it without hesitation. Then half and half for a while, then like you are doing now. I didn't really think this last stage ever lasted as long as the other ones, the milk taste was really there by the half and half and they moved much more quickly after that. She only needs about 24 oz. of milk a day so if she is tkaing a full bottle in the morning and evening the rest of the day I'd just try and use the milk in cooking and give her juice, no more than 8 oz's a day, and some water.