S.O.S. - need advice on how to adjust a two year old to newborn sibling

Kristina • Loving Mother. 2 year old baby girl. Baby boy due in March 2016. Happily taken since 9-2010!
My daughter, Jaunie-Ray is 2.5 years old. She's an amazing little girl - smart, caring little bundle of joy (usually). But since we had our son(3/22), she's (as expected) regressed in the worst of ways. I'm needing some advice on what to do cause I'm running out of ideas. She won't sleep by her self, she yells at me, tries hitting me, goes on "dinner strikes", I mean you name a "terrible two" behavior she's doing it. Time out doesn't seem to be doing anything, cause as soon as she's out she will do the same thing right over again. She isn't showing ANY aggression to her brother, just everyone else. 
I'm in need of any advice. Even if it's just wait it out. 
It's just heart breaking as a mom to see her child struggling and not knowing if what I'm doing is helping. Plus I'm only getting about 3 hours of sleep a night between waking up for nursing the newborn, and getting up to soothe her back to sleep.