Jealous over a new sibling??

So I'm really nervous about how my older daughter is going to react to a new sibling. She will be 23 months old when her sister gets here, and right now she seems pretty oblivious to what's coming her way (even though we talk about the baby in mommy's tummy and her new sister and all that). I just know right now she gets jealous if I give my hubby a hug and don't give her one... She gets mad if the cat sits in her daddy's lap.... And she tried to push her cousin off me when she sat in my lap and wanted me to read a book to her. She's very territorial when it comes to me and her daddy. Anyone else experience this? What did you do to ease the transition? How did it turn out?