I switched all my children at 8 months to a sippy. If she is already drinking out of it go ahead! The bottle is bad for their teeth and it is best to do it early so that they don't get too attached. I didn't do cups or bottles in the bed, except with water if they were thirsty.
I know a child that is 4 and still drinks a bottle with chocolate milk (from another culture). Seriously? That is ridiculous! I don't know why some people are so against everything the US does! It's not like the gov. will seize all bottles after a certain age, lol. Can you imagine sending your child to prek or kindergarten with a BOTTLE?
I put breastmilk in my son's cup until he was a year (I pumped for him the whole time anyway). He wasn't "attached" to his sippy - he used it to DRINK, not walk around with it hanging from his mouth like so many do with bottles! And, he was drinking from a regular cup at about 19 months. After that we only used the sippy if we were in the car for obvious reasons.
It is GOOD that she is drinking out of a sippy. There is no law that says she has to have a bottle anymore! Just give the same amount to her each day.
Good luck!