A.M.
It's ear infection or teething most likely. Look up ear infection signs in an infant, if she has several of them go to the pedi, if not, probably teething. She is 3 months old,she won't REALLY be in a solid bedtime till after a year old. Occasional teething, colds, ear infections, general fussiness and the excitement of a new skill (sitting, craling, walking) will keep her up randomly.
Good luck!