The 8600 (15.4" widescreen) can still be carried easily in a Targus notebook backpack or other brand that holds a 15" LCD screen. It weighs 6.9 pounds - about a 1/2 heavier as the 8600 was not designed for the Pentium M cpu so the case is thicker than it needs to be. The advantage of the 15.4" LCD is it is outstanding for all uses - widescreen DVD's at school, you can view more speadsheet area on the widescreen, and the viewing angle is better to the sides than a square LCD.
But the Dell 700M is much lighter due to much smaller LCD. However, make sure she actually tries the keyboard as the smaller the notebook gets the worse the keyboard gets in many cases. However, you can plug in an external keyboard in the dorm and have the more portable notebook in the classroom (using USB port) if she wants to do that.
Whatever she does, get a Pentium M notebook with at least the Pentium 725 1.6 Dothan CPU or above as that is the most recent technology for this Centrino line.
Note: The Compaq X1000 series I have and the sister HPZT3000 and also the Toshiba M35 series are excellent alternatives to the Dell 8600 as they have cases designed for the Pentium M so they are thinner and weigh 6.5 pounds and 6.2 pounds each.
The HP/Compaq also has a very good keyboard -- eclipsed mainly only by IBM notebooks.
See X1000forums and my other posts on this board. If she is a college student, she can get a student discount (APP) by ordering at HPshopping, a $100 rebate through 9/1/04 for any custom HP or Compaq notebook, and there are even more ways to save $.