Hi there
Your LO's sleep needs may have changed, some LOs start showing signs of moving towards the 2-1 nap drop at this age, although it is generally still early. If your LO needed longer than guidance A times or was low sleep needs or dropped other naps sooner than the "usual" age then I'd suggest looking up the FAQs on the 2-1 nap drop.
As a separate issue, it sounds like she has started to take milk in the night rather than in the day. Unless she is ill or you are BF on demand she probably doesn't need a night feed but it's a bit of a circle where she takes less milk in the day so needs it at night so takes less in the day. I'd wean the night feed so that it is 30ml less each night (then offer water instead) which means she isn't too hungry but also more ready to take milk on waking in the morning. Make sure her milk feeds are not dropping too much or offer some milky puddings (made with formula or breast milk or cows milk - and sugar free of course) or cheese to keep the dairy intake up.
Hope that helps