If Meg gets removed from the story of girldragongizzard, then the book doesn't even happen, because she's the narrator and author.
None of the other characters are likely to write a book.
We want to elaborate on this.
Even though the book doesn't get written, the primary event that prompted Meg to write it still happens, and a bunch of stuff still goes down.
Meg isn't particularly critical for that. In the first book, at least, she's not influential enough to really alter the course of history. She's made a small dent locally, and gotten some big actors to pay attention to her specifically because she's a loud mouth. But, by the end of the book, she hasn't changed much. The book is mostly about her growth as a person while she experiences the growing conflict the world is experiencing by suddenly having dragons in it.
If she's not there, there isn't even a reason for the book, but people still turn out to be dragons and take their true forms, and the city (and the rest of the world) is still thrown into some chaos about it. And her supporting characters are still friendly acquaintances who maybe end up befriending a different dragon, such as Whitman, Meg's direct rival, or Waits, who lives just a few blocks away under a bridge.
And there's certainly people, some dragons and some humans, who are off elsewhere in the world writing their own books about this.
When it comes to the planned sequels, all we can currently do is give you the titles and all that they imply:
How to be Megnificent
I am full of Megnitudes
Um. There might be at least
some scope creep there. Things that absolutely wouldn't happen if Meg wasn't there. But, we'll see what they are.