This is NOT fun, but it is totally normal. Not that it makes you feel much better.
Here's my advice:
Acknowledge as little as possible of the "bad" behavior. If she gets cuddles and the reaction of "omg don't do that" she is getting attention, which will reinforce her behavior. I used to tell my son "what? I can't hear you when you use that whiny voice...what? Where did that big boy voice go?" or "if you are going to hit me, I'm going to walk away." (even if it's two feet it reinforces that you are not going to give extra attention brought on by mean behavior)
Bottom line, she's worried she will be lost in the midst of another kid in the house. At least this has always been the case with my kiddos. As things get more real (baby items showing up, belly growing, etc) she is freaking out a bit. I would make it a point to give her some special dates with just you doing big girl things totally unrelated to the baby-and try not to talk about baby at all during those times, make it all about her. Be sure she has her own space (even just her room, or part of a room) that is the things she likes that are big girl things. I have to be careful not to let my baby things consume all the rooms in the house.
Look for and give her tons of praise for being a big girl. Catch her doing any type of "good" behavior and point it out and give her attention for that kind of behavior.
Make plans and stick to them to give her special attention after baby arrives. Let her know there are others that will help with baby so you can still have your big girl times together.
Point out things that babies can't do that she can...stay up later, play at the park, skip the second nap, etc. She will become aware of the value of being a big kid.
Hit the library, there are tons of big sibling books that are awesome...perhaps someone here can give specific titles...but even ones that just acknowledge her feelings are wonderful!
Patience is key-and expect relapses after baby arrives.
sorry I'm typing this very quickly as our lights are flickering in a naughty storm and i don't want my computer to die! lol-
in short if I can say nothing else...it will pass mama...all of my kids, even the ones that didn't talk to me for two weeks after they realized we were keeping the baby...they all got over it and are normal happy (for the most part
) siblings now.