1990s teen horror book?? Similar to Christopher Pike, but not him...?

I am wracking my brains trying to remember a teen book I read in the mid 1990s. It had an all blue cover, and it was set at a lake with a cabin. Something in the plot was that they were there to study for SATs or something, and all of the kids started dying. It ended up being one of the female characters who did it.....the author was in white or yellow writing on the front cover. It was reminiscent of R.L. Stine or Christopher Pike, but I'm not having luck searching through their books of them being the author. Any help?