Is she overstimulated during the day? Frequent sudden night screaming may indicate nightmares or night terrors. My friend's son had night terrors around 2yo, and it was quite an experience. But during toddlerhood, they tend to go through quite abit of growth and development, being more aware of their environment too. Info overload may cause their routines to go wonky. Do monitor and ensure she's still active and feeding well.