As far as I'm aware Tess Gerritsen is highly successful as an author, so it's not like she desperately needs the money to support herself, but I agree the lack of morals and basic integrity here is disgusting.
That said, from what I can tell, Cuaron's actual film Gravity seems to differ a fair bit from Gerritsen's original story. From what it sounds like, Cuaron seems to have taken inspiration from the basic concept to write his own original screenplay (which, one must admit, anyone who has ever done anything creative has done something like this, in some capacity), rather than plagiarise the story outright. So in this light it seems the link between Gerritsen's book and Cuaron's film is pretty indirect. Of course, I don't know the details so I'm unaware as to how similar both stories really are, so I'm not really qualified to offer an informed opinion on this particular matter. Either way, though, the implications this case has for the entertainment industry are pretty worrying, so I hope this pans out well.
Even so, why not just honour the agreement and honour the original agreement with the author? I mean, it's not like this film hasn't earned millions in profit...
Retribution (3rd place in BRAWL 2015)&Smeagol make the most of being surrounded by single, educated women your own age on a regular basis in college
AquaMorph I dunno women are expensive