S.H.
It has not been very long, since the new baby come home.
Kids need time to adjust.
HER life has changed, she is curious, she is excited, she is wondering, her brain is on overdrive thinking, she does not want to miss out on anything going on, she has "emotions" for which a child this age CANNOT understand and, developmentally, a child's emotions are not even fully-developed yet nor their capacity to "cope" with it.
LOTS of things on her plate and upon her shoulders and in her life... So, this is naturally hard for her and a transition to a "different" life for her.
Patience. She is still adjusting to it all. Life is not the same for her. BUT... keep to regularity and consistency in HER routines and habits... a child needs that. She is not being "naughty" on purpose... a child this age needs help to cope with it all. They don't know how, on their own.
Its okay. She will adapt in time.
ALSO though, over-stimulation and getting a kid over-tired can back-fire. Over-tired kids actually have a HARDER time falling asleep and they wake more. Same for over-stimulated kids before bed or nap. ALLOW her to "wind-down" before nap or bedtime. Even up to 1 hour beforehand. Incorporate a "wind-down" time INTO your regular pre-nap or pre-bedtime routine. And make that time a "quiet time"... not a hyper active time. She obviously NEEDS more time to wind-down.
My kids, would NEVER be able to sleep when my Husband would horse-play with them prior to bed. It just got them ALL hyper and wound-up and NOT "able" to sleep... when I had previously managed to get them "quiet" and simmered down. Finally, my Husband realized that. He thought, that getting them all active and tired right before bed, would make them sleep. Nope.
Kids NEED NEED NEED a time to wind-down prior to naps or bed.
All the best,
susan