I wasn't aware that a book needed to make me feel positive and happy in order for me to enjoy it. I tend to be drawn to the darker stories, because I enjoy the "what if" aspect of life....
I'm sure there are several others, but the only one that I can think of right off the top of my head would be Rita Hayworth and the Shawshank Redemption.....it left me feeling very happy for Andy and Red in the end.
Oh.....and I wouldn't worry much about her wanting to read another book to be sure she likes SK....she's already hooked, she just needs to confirm the addiction