And you also might want to read this from the sleep foundation - http://www.sleepfoundation.org/article/how-sleep-works/how-much-sleep-do-we-really-need
Average sleep needed is 10 to 11 hours. Just because she is so active during the day does not mean she needs more sleep at night. In fact, it could mean she has a harder time going to sleep at night.
A death may well have affected her especially if it was a close family member .Iits very normal and common for an older child to feel usurped, I would try an 8pm bedtime see if it makes any difference , where does the baby sleep and is baby asleep or awake when she goes to bed ?.Stories are really great before bed .maybe some soft music to slip off to may help ..this time will pass it is a trying moment in time ...
We have always sent her at 7pm because she is so active in the week. We read two stories to her at night. Everything to do with baby we include her. We made a big deal of the birth for her and even bought her a prezzie from baby. Its so hard. Like tonight she has screamed all night except for when we were with her. And then as if like magic she just said im goin to sleep like a good girl now. How bizarre. We have also had a death in the family which important wondering if that ha affected her.
Margy is right on. I would also add - do you just send her to bed? At that age you can still read to her for awhile. Its educationally a great thing to do. Its also wonderful for bonding and helping out with some of the issues that Margy mentioned.
I do think you have hot the nail on the head and she is feeling left out, can you make it 8pm to go to bed 7am seems early to me ..Does she get plenty of attention now there is a baby around? Focus on her positive side, let her help with baby and reward her with praise for helping.. one to one time is also good .