Drama queen for a sister?

Let me start by explaining my sister is 2 and I watch her pretty much all day long (I'm out for the summer from college, and my hours are crap for work). But while I was in school I would have her till noon, and she would still do this. Every morning she wakes up " I want chocolate milk, I no feel good" and repeats it every minute until milk is delivered. If she doesn't get what she wants for breakfast she'll either throw it or shove it then start screaming bloody murder.

She usually shares really well and behaves well, but there are times she pitches tantrums about sharing or if my son (1) has a toy she wants. At times she'll go over, kick him or push him out of the way and take it herself. She goes into time out then, but then will tantrum in time out, then refuse to get up and when she does she starts crying "I want mommy" then tantrum more.

She doesn't sleep in her own bed, she doesn't go to bed till 9 or 10, and on top of that she sleeps with our mom. I (21) had her sleeping in her own bed then she got sick one day and since then (she's been better, it was in March) she's been sleeping with our mom. She tantrums and screams if she has to go in her own bed, to the point one of two things happen. My mom goes to get her, or she comes to us (my brother (23) and I) where ever we are in the house. So then she ends up in my brother's room (unfortunately when she ends up with us she'll stay awake till 12) till she falls asleep and then he'll haul her to her bed, wrapped up in his bedding.

I know it's probably just the terrible twos but it's getting on everyone's nerves.