V.W.
Well, obviously, she no longer needs the nourishment from nighttime feedings. Have you thought about just telling her, no more feedings during the night.
It worked for daytime, nighttime shouldn't be any worse. I would suggest, like Melissa R. mentioned, that you provide her with a "lovey"... something to snuggle with during the night. You can take her and let her choose it. You could even tell her the new plan, followed immediately by, "so today we are going to go find a lovey that you can sleep with". Valentine's Day is next week, so there are going to be tons of fluffy, snuggly, stuffed animals available for her to choose from. :)
And, by the way, she doesn't need to have a sippy cup in order to let her have only water during the night. You could get a small cup (whatever she uses during the daytime) and fill it with only a small amount and set it on her nightstand or dresser, for "just in case she gets thirsty."