Silly me, thinking it would be in the laboratory section. 
But, since this is a magic item and not an independent item, I should be good with what she's doing, then. R: Voice, using Fiona's voice.
(Alexei will be so proud the first time she whips that out at fighter practice 
)
And anyone who has the theme to Danger Mouse stuck in their head multiple times every day can't be all there, right?
So, something Fiona said in her conversation with Korvin (no, not that conversation, this one was actually relevant) got me to wondering.
The only Muto book we have, In Flux Veritas is "only" Level 12. I can't find Fiona's start-of-play character sheet, but she had a Muto score of 10 when she was Gauntleted, 26 years before the game started. So, she most likely already had a Muto in the 13-15 range, and thus has never been able to read that particular book since the game started.
Now, since she has a Muto of 17 now, she would gain no benefit from reading In Flux Veritas. But you can't write a Commentary on a book unless you've read it.
Would the troupe be amenable to stipulating that Fiona has read the book and thus can write a commentary on it, or would they have Fiona read the book (with no gain)? (She would gloss it, as well, and she may anyway, but someone beat her to it )
The description of In Flux Veritas starts with "Written by the apprentice of Mutante of Mercere, this is often considered to be an essential book on the Technique of Muto." Seems to me that it would be widely available; it's not a stretch to think that Fiona read a copy during her apprenticeship even, or early on in her Hermetic life.
I'd be fine with her wriring it.