You really do need to get rid of the milk in the bottle, mom. She can end up with a mouthful of cavities. No more milk at night, period!
Apologies to your 4 year old, but I'd let her scream about water being in the bottle, to be honest. Maybe you can put little ear plugs in his ears.
This 5 times a night thing means that she has not learned to self-soothe at all. That's a real problem. You're going to have to bite the bullet and sleep train her.
Figure out which method you want to use. Whichever it is, do NOT pick her up. If you do, then you are substituting yourself for the bottle. She needs to learn to fall asleep on her own. You can either throw away all the bottles so that you don't have ANY to give her, or leave a bottle with water in it, laying in her crib. I would assume that either she will ignore the bottle with water, which means that she is weaning herself from the bottle, or she will switch to the water. I would not bring a bottle to her. By you "giving" her anything when she screams, she is expecting YOU to put her back to sleep. She can find that water bottle in the crib on her own.
At the same time, I think what I would do if I were you is put a chair (something a bit comfortable) in the middle of the room and come sit in there, faced away from the crib, and don't talk to her AT ALL. Just come in and sit. She will cry, but if you do not move, she will finally lay down and fall asleep. Eventually, move the chair closer to the door. She should stop waking up as often because there is really nothing to wake up for. The key is to never go to the crib and interact with her. Whatever you do is giving her a REASON to wake in the middle of the night.
This is hard, but my goodness, you people need your sleep! Bite the bullet and just do this thing, no matter how much she cries. Be 100% consistent - if you aren't willing to keep doing it every single night, don't bother to try. Being inconsistent will just make her cry more and more.
Sending you strength~
Dawn