D.K.
CONGRATS! That is so exciting.
One thing that helped my daughter with her little brother coming along was getting out her baby photos/videos and showing her she was that small, how I had to take care of her when she cried, why babies cry, (because they cannot tell us they are hungry or wet) and that she got lot's of care when she was a baby too. Then we got our daughter a baby doll of her own that we gave her from her new brother so she could take care of her baby when I had to tend to her brother.
I can say more then anything she was extremely doting to him, she would yell at me if I didn't pick him up immediately when he cried. Make sure if you and she are up when the baby is sleeping you give her lot's of snuggles and extra one on one time. I would put the baby to bed and then hang out with my little girl, just she and I! :)
Still do, her brother goes to bed earlier so she gets that time with me.
She will have moments when she wants your attention and you are feeding the baby and all of that. I just tried to let my daughter know I would love her to sit with us while I fed him, to get me a diaper and be my diaper holder when I changed him. She was great about it. It was when he was old enough to pull her hair and get in her stuff that things went different, hee hee...which is NORMAL! :)