Wuthering Heights - Emily Bronte
The Mill on the Floss - George Eliot
Bleak House - Charles Dickens (not quite as tragic as the others.
Or if she likes more modern books, I'll try to think of some, but usually I go for more cheerful things now. When I was 17 I read lots of victorian literature including the ones above, and lots of other fairly bleak stuff (I wasn't exactly a cheerful teenager!), but it's hard to remember at the moment. If I think of any more when I've looked at my bookshelves I'll add them.