Unfortunatly in practice you should notice a difference in a couple of days, in adults you do, I have been on losec before and it does only take a coupleof days to work. But in the babies we find that it is about the 2 week mark, maybe because it is more behavioural or because they can't tell you oh that feels OK now, it also depends on how long and how severe it is. If she is on the 20mg now, I would keep her on it, it won't do her any harm. Wait until you see an improvement and then you can always lower it.