She probably didn't have much choice in the negotiations. She's not J.K. Rowling, who can literally walk from any deal she doesn't want because she's got more money than she will ever need, and a huge, loyal fan base.
I remember reading some old interview by Stephen King. He said at the beginning of his career, he was so happy when studios approached him on making many of his books into movies. He did it for the money & the exposure, taking his career to a new level. He hadn't understood how much of his rights he had signed away. Or how the crap movies would also be attached to his and his books' image & reputation.
After they massacred many of his books (on massacres
) he swore he would never let that happen again. He'd rather not have the movies made at all. It's rare to see a Stephen King movie now, or any project in which he also isn't one of the executive producers where he can maintain some artistic control.