L.,
What your daughter is doing is normal, as babies eat more and more solid foods they tend to cut back on the amount of bottles they drink. The other thing is your daughter's taste buds may be changing, she may not like the taste of the milk. If she is on whole milk you could try adding a drop of maple syrup and vanilla, just only enough to make is taste different. We did that with our third child, he decided he didn't like the taste of milk so our pediatrician suggested we try that. He still is not a big fan of milk and he just turned 21, but whenever he drinks milk he puts maple syrup and vanilla in it or makes milkshakes. Babies are like us, their tastebuds change, just wait until she decides she won't eat anything green or my favorite, eats only pasta and potato bread with creamy (and I mean you have to whip it in front of them) peanutbutter for months on end, talk about getting worried. LOL My 9 year old son refuses to eat fruit or drink fruit juices, never has liked them since he was a toddler, it drives me nuts. I love fruit, vegetables, nuts, beans, this one is a meat potato and corn kid. Bottom line she will problably outgrow not drinking milk, but if you are that concerned call your pediatrician.
Hugs,
T.