In reply to stroppygob:
The 'best' windows laptop is probably still the MacBook Air. If need be then you can always install Windows on it. The hardware is just 'optimised', assuming you want light, strong, fast, screen, trackpad, battery life all to be very good. I have a couple of died in the wool PC using colleagues who have ended up with them and just run Windows on them. Seems like a waste to me, but there you go.
The thing that equates to 'fast' is a solid state drive for storage rather than a (spinning) hard disk drive. MacBook Airs only have SSDs, so they all feel fast even if the numbers of processors seem higher in other competitors.
Other machines are available but it is commonly held that the MBA is the best balance of all the above (especially the trackpad, light and fast bits). If she has a desk then a cheap external monitor, keyboard and mouse are easy enough to set up.
If she is doing a double honours degree she can cope with the couple of hours needed to learn a few tricks to the new OS. There's very little new out there - a good Linux distro, Windows 8, and OSX Mavericks all work pretty much the same from the point of view of a busy undergrad.
The University should be able to provide the requisite software at bulk license costs - it sounds like she will need a few things.
For a science undergrad then she will clearly need Microsoft Office but may not need stats beyond Excel. If she does then SPSS is often bulk funded by the Uni (much better than the 1000s of dollars charged per license otherwise). EndNote is handy if it can be got on a bulk deal but again not worth the 5k or whatever it is they charge these days for it.
If going down the Mac route then I would absolutely recommend 'Papers' for managing scholarly articles and citations - much cheaper than EndNote, much easier to use. Keynote is like Powerpoint but a zillion times better and again good value at about 25AUD. But advanced stats and complex citation managers are more postgrad stuff usually.
Almost all Unis will require antivirus software to be installed and should provide this (probably for free). Not an issue with Linux and to be fair not much of an issue on Macs.
Also put some money to one side for a backup solution that really works. Otherwise disaster will strike, usually just when the project is due in... I look upon this as being something Macs do quite well - in as much as it can all happen automatically without user effort.
Hope you find something that fits
Cheers
b