Plagiarism, while it's scummy and fattening, is not illegal. The makers of the TV show can't stop her, unless she's dumb enough to copy chunks of their dialogue word-for-word, or nearly so. Goodreads don't care what authors publish, as long as they behave themselves on the site. (And even if they did care, all they could do is ban her from the site). That leaves the publisher. If you can prove your assertions, and they have any integrity, they'll cancel her contract, withdraw her books from sale, and make sure she never publishes with them again.
EDIT: Yow... every time I think I've learned the limits of human stupidity, someone proves me wrong. If she's copying chunks of dialogue from the show, that's not just plagiarism, but copyright infringement too, which *is* illegal. I'd tip off the TV channel that broadcasts the show and the production company that makes it. Either or both could have standing to sue. The production company might care more about protecting their assets, but the TV channel probably has more expensive lawyers. If you're feeling charitable, contact the author's publisher as well, to let them know about the incoming lawsuits. That will allow them to pre-emptively sue the author for breach of contract and recovery of the damages and lawyers' fees that the TV people will extract from them.
(When you sign a contract to publish a book, there's a clause where you promise that it's entirely your own work, or if any of it belongs to someone else, you've obtained the necessary licenses and paid any necessary fees. That's evidently not the case here, so the author has broken the terms of her contract. There's often also a clause where you promise to cover any costs the publisher incurs for something that was your fault - such as stealing someone else's work.)