(“them” being the Caroline Lawrence books whose violence I was disturbed by)
An adult. I read a lot of kids’ books. A good story is a good story, and this is a golden age of illustrated books. (Did I mention pop-up books?)
I think that is because we grown-ups know how horrifying this stuff is in real life. Violence that may seem cartoon-ish in storybook is more affecting in a newspaper.
(me: “commit crimes so masterly that only Sherlock Holmes can solve them.”)
Irene Adler didn’t really commit any crimes. But plenty of other woman characters did. Will not spoil the stories by posting here which ones turned out to be the guilty parties … 
At that age I was reading Christie, Sherlock Holmes, and Encyclopedia Brown. I just really liked mysteries. I don’t recall anything inappropriate in any of those books (there was maybe some cocaine use by Holmes, but it kinda flew over my head at that age because it was euphemistically-described). However, my grandma and a couple of my friends had massive collections of romance novels which I was reading on a regular basis–your daughter may be doing the same in the near-future. I don’t think there’s anything wrong with them, but then I grew up reading them. No more dangerous or impermissible than a 12 year old boy looking up porn on the internet. YMMV.
Agreed that Agatha Christie stories would be suitable for a book-loving 10-year-old - and another vote for the Sherlock Holmes stories. Deservedly classics.