Firstly don't feel bad about giving your child a bottle of milk. Some children are breastfed for much longer! However it may be hard to break the habit of bedtime = bottle of milk. Maybe you could start with getting her to drop the morning bottle & progress from there? At some point though if she is showing no signs of giving up the bottle you have to make the decision for her bcus it is in her best interest & she will eventually learn to go without it.
We have only just weaned my son off his night time bottle of milk. What a nightmare! We tried every type of sippy cup & transition bottle we could find but he would just throw it on the floor. He drinks water & juice from a drinking bottle/cup but he would not accept milk in anything but a baby bottle. We gave him some leeway bcus he was a preemie & suffers from chronic ear infections so is always sick & when he is sick he would only drink milk & water & no food.
It felt like he would never give up his bottle! About 2 months ago I found a transition bottle for sale at Coles & it has a plastic spout (I think Nuby or NUK) but no teat. They just rest the plastic bit on their lips & suck. We figured we would give it a go & told him it was his big boy bottle - no more baby bottles but we were expecting him to throw it on the floor as with all the others. For some reason he accepted this bottle! He would drink his night time bottle at first but for about a month now he just doesn't want it. We are having trouble getting him to drink milk from a sippy cup but he has plenty of calcium in his diet milk with cereal, plenty of cheese, yoghurt, custard, salmon & veges like broccoli & spinach so he will be ok. I think he was just ready. I also think in some ways I didn't give him the benefit of the doubt & just kept giving him his bottles of milk.
I was really worried about the effects of tooth decay from the sugar sitting on his teeth bcus it can & does affect their teeth. DS brushes his teeth (quite well actually) twice a day, drinks lots of fluridated water after meals, didn't play, suck or carry his bottle around in his mouth. His teeth appear fine - no signs of decay that I can tell. Phew!