The notion of an "original" product causally linked to the WB-produced film _Gravity_ assumes facts not in evidence.
Gerritsen alleges that the film she worked with Katja on formed a basis for WB's film by dint of Cuaron's involvement in both projects. In the earlier project, Cuaron is alleged to have been "attached" to the project. In the WB production, Cuaron and his son wrote the entire screenplay.
The film term of art "attached" doesn't have a precise meaning. "Attached" can be an indicator of someone's commitment to a project --- a spectrum from "aware of" through "interested in" through "attached" through "committed". It could also mean that the person is sponsoring the project and shepherding it through the development process.
At no point does Gerritsen allege that Cuaron's screenplay included any of Gerritsen's writing. At best, her claim is to the storyline --- the ideas --- of the WB film.
What Gerritsen is saying --- informally, in explaining her reason for deciding to pursue the case, and also in rebutting WB's claim that Gerritsen had already conceded the film wasn't based on her work --- is that she had always felt that the WB project had an uncanny resemblance to her own story, but that she didn't have a smoking gun until she discovered Cuaron has been "attached" to the earlier project without her knowledge.
The fact that the author of the book and a contributor to the punch-up of the screenplay was unaware that one of the most famous directors in Hollywood was "attached" to the project suggests that the word "attached" was meant in its more casual meaning.
But the fact that Cuaron and his son wrote a screenplay involving a novice astronaut marooned on the ISS after being made aware of a project with a similar story suggests that there's some link.