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Long time since my DCs were this age but think they wake out of habit. With your DS did you try cooled boiled water instead of milk? When DD wakes and cries, don't put the light on, maybe use the landing light instead, go in but don't talk to her. Give her the water and settle her down again. A few nights of this and hopefully she'll sleep through.
I never risked another trick which is to gently wake her an hour before she normally stirs, and then put her back down to sleep. The idea being, baby goes back into a deep sleep causing her to sleep through the usual dawn chorus wake-up time. This is meant to break the habit if you can do this a few nights' running. I hate being roused from sleep myself so never had the heart to try this.