There is something called "Warm Milk" by the brand Animal Parade. They make kids vitamins.
This, is supposed to help kids calm/sleep..... before bed. Like a nice warm cup of milk.
It is a chewable vitamin.
You can see it on Amazon... and read the reviews there.
Also, if she is over-tired.... does not nap all day.... then by bedtime... she is just OVERLY tired more. And then, this makes falling asleep/and staying asleep... worse.
Major sleep deprivation.
"Tired" kids.... get very moody.....
Also yes, make sure she does not eat junk.... before bed or all day. Hopefully Daycare feeds the kids... healthily.
she knows... that at night... if she acts this way screaming demands... that most likely... she will get what she wants... because you/her parents do NOT want her to wake up brother. And, so, getting what she wants... will be her parents quickest way.... to make her quiet.
Also you just need to sit her down... tell her PLAINLY that her behavior is NOT acceptable. It is not.... nice... and not.... allowed.
The more that it makes people placate her.... and that people try to rationalize with her and whatnot... to her... probably... it just means that she is 'controlling' everyone....
But IF she is uncomfortable during bed, or had a nightmare... then she MUST learn... how to... communicate that... WITHOUT yelling.
She seems to be in a real moody mood.... due to tiredness AND perhaps, whatever 'junk' she may be eating all day at Daycare. If that is the case.
All I know is... my daughter, gets major fussy... if she is hungry, if she is tired... and has not slept well.
So... those are her triggers.
See what your daughter's triggers are. Or, if she is just acting that way to act that way... then you must... just tell her NO. And walk away. Or she will keep doing it.