D.D.
Talk to her a lot about the baby so she knows it's on the way. I have a 7 week old boy and a 21 month old girl. I tried to prepare her but it didn't work. She was very jealous and the first month was awful, she would try to hit him and be very mean.
Work on teaching her what "gentle" is... my daughter would touch the baby and be so rough. I had to work with her about what gentle meant and now she gets it and is so much better! She touches him very gently now.