It kind of depends on her college plans.  Her college may have certain requirements.  Some may require a computer be purchased through them.  For an example see http://www.rose-hulman.edu/admissions/laptops.htm They do this for various reasons, one of which is software.  It guarantees the student has the specialized software needed and the license is valid.

Even if the school does not require a bundle be purchased, often they have a special promo of some kind that you will have trouble  beating at retail.

Get her the fastest CPU you can afford and a minimum of 3 gig of RAM.  No, make that 4 gig of RAM.  Hard drive size is unimportant.  It will never be big enough but whatever is in it will be adequate.

Whatever you get her, buy the longest life battery available and get a spare power supply.  My computer geek brother told me this when I bought mine and  I wish I had listened.  One PS stays at my desk and the other (yes, I bought another later) stays in the computer bag. I would also suggest a dock of some kind.  I have an external keyboard, wireless mouse, printer, network cable, all connected to my dock.  I set the laptop down, plug in my power and one USB and everything is connected.

I mentioned Rose Hulman's requirement to buy a laptop bundle through the college.  The RHIT freshman class of 2008-2009 laptop model is the HP 8510w Mobile Workstation: