That's the lady whose real life daughter was murdered correct? If so, the one I remember most that I think was hers was about these Native American twins who did astral projection & the one w/ the "bad" life was trying to steal the one w/ the "good" life's identity or something & of course the one w/ the chick who has to join the witness protection program.I love Christopher Pike books! Sometimes I go to the library to read them. I like Lois Duncan too.
The first author that comes to mind for me is Christopher Pike, I think I used to read his books when I was in middle school a few of the ones I remember are Slumber Party, Chain letter 1 and 2, Whisper of Death, The Midnight Club and about a million others.
i bought a bunch of christopher pike books on ebay a few months ago. they're just as good now as they were when i was a kid!