Yeah... she was that way from the "Mutant Massacre" through the "Fantastic Four vs. the X-Men" miniseries. Terrible writing, BTW. But for those of you who fancy Shadowcat, she spends most of the mini without any clothes on.
Terrible writing? That mini-series and the Marauders' Massacre issues just before it are still my favourites in Marvel History along with the issues where Magneto confronts Rachel's survivors' guilt (196?), where she confronts the Beyonder (204?), and where Wolverine runs her through (208?). The stories were a bit melodramatic perhaps but I don't think they were ever able to create such delicious bleakness again. PTSD Rachel was my favourite character (partly because I was such a fan of Jean and pre-Phoenix Rachel was just a seriously flawed version of her).
The Kitty Pryde & Wolverine series was quite good too as it charted Kitty's passage from child
(Sprite/Ariel) to brutalised adult (Shadowcat).