Throw them away, let her watch you put them in the garbage bag, have her even help, seal the bag and say "bye bye bottles" take it to the curb. Be matter of fact, if she cries it won't last long, just remind her what a big girl she is now. She will get over it. She knows you will cave and give her a bottle. Not only is it bad for their teeth is a habit now. Take her to Target or somewhere like that after you do this have her pick out some fun strawed cups. If she refuses sippies it is mainly because she knows you will give her a bottle if she resists. A day or two without milk will not hurt her, she will be fine. Even a week without milk will not hurt her. Just make sure she is getting her dairy (for calcium and Vitamin D) from other sources like yogurt and so on. You have to stand tough she will recover. Both of my kids LOVED strawed cups, easier on the teeth too by far. Both of my kids waved bye bye to the bottles on their first birthday and never asked for them again.
Good luck.