I'm guessing she's whoever Barbie was talking to on the phone in the beginning of the first episode. That's just a guess.
She's in there to play the female villain - sort of the feminine version of Big Jim. She adds a bit of spice by kissing Barbie and right away we think - oh oh - poor Julia she's going to get hurt (well maybe that is what people thought). I like Barbie and I think he plays a good hero. Anyway at this point - who knows? To tell you the truth I have forgotten the original book by now. I am sure it is light years better than the TV series (in fact I am positive of it). I remember getting UTD out of the library and I don't own it yet but I do plan to add it to my collection.
You really cannot compare UTD the book to UTD the TV series because like Mr. King says - well anyway look up above under the 'Under the Dome' main heading and you will be directed to a link to read the author's comments about "Why the changes?" (by the way no bounce no play I am replying to nebogatoff but wanted to include your spoiler! :y::biggrin2:)