Follow-up: Does anyone know how to best host this site?
a) with less than 50 users all-time
b) easily updated daily (blog-style) by a 7 year old
c) is approximately free
Wordpress with her custom theme seems to fail C.
Github pages / Jekyll is failing B
I responded to you on Twitter but I would go for Tumblr. Easy to maintain, and makes it very easy to publish media-heavy posts...which, even if your daughter is the next J.K. Rowling in terms of enthusiasm for the written word, Tumblr hits the right mix of decent flexibility and dead simple UI. I maintained my own Wordpress site but ended up posting much more frequently to Tumblr.
I now am basically 100% Jekyll and Middleman...but having tried teaching Github Pages to college students...I'm skeptical that it's easy enough for a child to hack around with and get the same amount of enjoyment and productivity that she would out of Tumblr or WordPress.
(Apparently Ghost is pretty good too but I've never tried it)
Livejournal is still the best for writing posts and having discussions on. Takes no effort to keep going, and has threaded comments, supports images and videos, and basically just works:
Wordpress with her custom theme seems to fail C. Github pages / Jekyll is failing B