No, she's absolutely wrong about this. The book is based very closely on Feynman's lectures. He wrote the material and gave the lectures. Other people edited that material into book form, but Feynman did the lion's share of the work.

Saying that Feynman didn't write the book is just dishonest, unless you immediately clarify afterwards that Feynman did indeed write almost all of the material in the book, in something very close to its final form.

You should watch the whole video. From memory, the video author claims that the books are not based directly on the recordings nor on material that Feynman wrote himself, but rather on lecture notes written by another professor who had to cover for Feynman (who is also listed as one of the authors in the book). She also mentions how those lecture notes from this other professor correct some small mistakes Feynman made in some calculations and diagrams from the lecture. Her claim is that Feynman was not the person who actually wrote the text of the book.

Seems she isn't interested in dragging a bit of fame and recognition her way.

It's a low effort way to do that when the other party cannot defend himself.

I mean, for the most part the book is an edited transcription of what he said at the lectures (or, in some cases, what a guest lecturer said). But the lectures weren't scripted, and we know this because his lecture notes are preserved[0] and they do not contain anything like he full text of even a single lecture. They're just lecture notes, not a script. And of course, the book also contain a lot of example problems and graphics - those are mostly the work of Bob Leighton, I believe. There's a reason the book has had so many errata corrected over the years: it was never written and edited in the way a book manuscript would've been written and edited.

[0]: https://www.feynmanlectures.caltech.edu/Notes.html