Hi mummy, it’s normal for newborns to feed more, it will get better as they grow (sleeping time stretches). My soon to be 3m old is also drinking once to none overnight.
Start by giving lesser amounts, if she wants more, top up little by little to avoid wastage.
For leftovers:
For formula, please discard in an hour. For breastmilk after 2 hours, can save in storage bags for milk baths.
Datchayini