The AAP now recommends waiting on solids until 6 months, so I would hold off on that for filling her up. It's possible that she is having a growth spurt & needs to eat. In fact, an infant's wants ARE needs - they don't yet know the difference.
With my son, as soon as I figured out his routine, it changed. I wouldn't be too surprised that things have changed. Also, babies wake frequently throughout the night to help prevent SIDS, so keep that in mind.
If you are nursing, she may not wake so much (nor you) if she sleeps with you. I'd be happy to share safe co-sleeping tips. If you're using formula, maybe you could have it already made? (I don't know how long it lasts or when you go to bed).
Last thought - crying it out is now known to cause brain damage, so please don't even consider it! I'll send more info if you're interested.
Good luck! I know it's hard to parent at night, but an infant's needs are no less intense at night than during the day.