Lucas was my dummy addict! The girls were fine, nap time and bedtime only until they were four, then we worked on getting rid of it altogether. Never had a problem. Lucas on the other hand would have his in all day every day if he could get away with it!
Start slowly, tell her she can have her dummy after a certain time. Seeing as they have no real concept of time at this age, you'll need to be creative! With Lucas teletubbies was on every morning and finished around 10:30 I think, so there was no dummy until that had finished, then we moved it again to after the next programme, then it was no dummy until after lunch. He was completely fine with that, then he started nursery, which was handy as he had an afternoon place, so suddenly we had no dummy until after nursery (which was 3:45), then none until after dinner, then it was after bathtime and finally at bedtime only. Yes it took us months to get to that stage, but we got there! He was slightly older than the girls when he gave it up completely, but he was dummy free by the time he was in his pre-school year.
Obviously you have the added 'problem' of having two littlies with dummies, so I'd try going down the starchart route too. If she can last until her given time each day she gets a sticker/star and if she manages so many stars in a row she gets a treat (watch out Pound World Fee's stocking up
). Does she have a morning or afternoon place? If she has a morning place you can take it slowly as she'll be able to have it at lunchtime, but if she has an afternoon place, you'll have to change dummy time a little bit quicker.