No milk, Cannot sleep

Pie has the habit of drinking milk (from the bottle), and then only falling asleep. I would love to break this habit, but then what is called a habit ? It's something that needs time (and a super long time) to break it.

Thus when my Mum brought her to see the doctor (due to Pie complaining of stomach ache), doctor's advise was not to drink any milk (is there a link that milk can cause gas ?). You know what Pie's reply was ? She said "No milk, Ashley cannot sleep!". Which is very true. (By the way, it was her 2nd visit to the doctor in a week - her 1st one was due to fever)

Which makes me think that I must try to change Pie's habit of drinking milk from the bottle (and has to be done soon). I tried to get her to drink from the bottle which has a straw instead, but after sucking a few times, she grew tired and refused to drink, thus had to resort back to putting into her normal bottle. Anyone can help ?