If she's got the budget and lifestyle for it, I would highly recommend getting an $800-900 uATX/ITX for gaming and work and a $500 laptop for portable work. uATX and ITX builds are quite small, thus it's not a hassle to pack and move it whenever she moves dorms or comes home to visit for a week etc. Plus a desktop system will be much cheaper for better performance and will be upgradeable, meaning it's more like an investment; rather than laptops which are used until they're obsolete then thrown out.
Just to reiterate what Robert said: Don't get Windows 7! Windows 8.1 is better in many ways. If you can't get used to the layout just download Classic Shell for free and it'll run on top of the Windows Shell, altering the layout to what you're familiar with while keeping the many benefits of Windows 8.1. Also, being older, Windows 7 is closer to no longer being supported by Microsoft; Windows 8 still has many years of support/updates to come, which means it's a better investment. Not to mention I hear Windows 8 owners will get a free upgrade to Windows 10 when it comes out.
As per what kind of budget you'll need, that depends on what she uses it for and what games she plays. More information = better. Higher end gaming you're looking at a minimum of $1500. Lower/medium end gaming you'll be closer to $1k. A need of hyperthreading will generally increase these numbers as well.
As per your question about 3x RAID 0. It's basically mirroring the information on the SSDs and uses a controller to read different parts of the files from different drives, thus increasing your read speed. A 3x RAID 0 would theorectically give you 3x sequential read speed (i.e. 500mb/s -> 1.5gb/s), however the overhead associated with the controller makes it slightly lower than that. The reason I generally don't recommend RAID 0 is that it doesn't tend to help with small random read, which is generally the most common type of drive reading an average user will do (it does help large queue random reads but those are much more uncommon than small queue random and sequential read, thus negligible imo). Because of all this, I personally would rather have 750GB of NAND flash mem rather than 3x 250GB RAID 0.
This post was edited by SanityWasHacked on Oct 23 2014 11:01pm