I have never (unless he was sick) given my now 3.5yo son a drink in the middle of the night (well, except when he was under 3 months). It is unnecessary and it just becomes a habit. Most everyone wakes at least slightly during the night and your little girl has found that if she wakes and cries, you'll come in and give her a drink. It's not that she's thirsty- the drink is just the excuse to see you. If you continue letting it go on like that, she'll always do that sort of thing. Unless she has some sort of illness where her body needs the liquid, which is very unlikely, I say you're just giving her the attention she needs. Not to say you should let her cry and ignore her- I don't believe in that. With my son, if he woke up and needed me I would go to him and pat his back or rub his head, something, but I wouldn't pick him up. I read that the main problem most babies have with separation anxiety is around between 13-18 months or so. Ours did just that and we actually bought a cot to go in his room and one of us would lay on that until he fell back asleep. We felt it was necessary to get him through that hard stage and it worked. He has always been a great sleeper except for those few months. Just my opinion.