Will Time Capsule work on a college dorm's WiFi network?
Solution 1:
She could probably tie the time capsule into a ethernet line in her dorm (I assume there is a wired option) and then set the time capsule to be on bridge mode (where it doesn't issue a new IP adress but rather passes the one issued by the school's DHCP).
She could then use her Time Capsule (which is also a wifi router) to have her own private wifi locked down for her dorm, this is what I do in my house as Telus doesn't offer DSL modems as a standalone.
Solution 2:
The best answer for laptop backup in a college dorm is NOT an Apple Time Capsule. Everyone here has already examined why that won't work well at length.
If you haven't bought the Time Capsule yet, don't. Go with a simple bus-powered USB or FireWire mobile hard drive, like the WD Passport. Get one larger than the laptop's internal drive and configure it for Time Machine.
If she just leaves it on her desk and learns to plug it in whenever she's working there with her computer, she'll be covered. As a recent college student (who used to advise his dorm-mates on that sort of thing), I'll attest that this is pretty easy for most people to condition themselves to do, and if it doesn't, it'll only take ONE case of data loss to teach them soundly how to practice good backup habits.