Time to sat "bye-bye" permanently to the bottles...throw them away and don't look back. She still has the option of using them, so she has no incentive to use the sippy cups.
Yes, she may balk and throw fits, but she'll adjust as long as you don't give in. My guy went cold turkey at 13 months with bottles AND pacifiers the same day, his ped had said the day before it was time to stop the bottles, so I had started no bottles that morning and at bedtime couldn't find his "suckie" and refused to go out or send anyone to buy one. He fussed a bit the first night, asked a couple of times over the next couple of days for it, but never the bottles, and within 3 days he was a sippy cup master.
Get the cups that she holds like a bottle, with no handles, I found he liked those best, I think it gave him a "bottle" feel. I also had 3 of the same cups in different designs, one each for milk, water, and juice, and he learned the difference.
Hope this helps : )