I decided to do something that I thought would be interesting. It was. Turns it out it was also a hard thing.
I went through the 29 threads Nyx has been in so far... and added up the word count for each and every IC post. Of course, there are actually a few more threads she's been in that didn't make it onto my thread tracker for one reason or another (the main reason being that I couldn't find them). In addition her biography along with all extra writing for her was excluded. So, no, her letters don't count.
I'd put all of the text in a spoiler, but, well, blog posts have length limits. And Nyx's stuff far exceeds said limit.

ORIGINAL ESTIMATE: 100,000-120,000
While I've written less than I had thought, adding in the various 'extra' things I've written for Nyx would add at least another 20,000 words to this. That would include things like short stories/scenes (some of which I'll be posting here at some point), her biography, and the songs/poems written for/about her.
Overall I'd be surprised if any of my other characters could boast as impressive of a word count. So... cool?
I've wasted so much time on this little Babu, wow