TEE1 makes a good point. The light is a small piece of a big puzzle.
In order of priority:
1) Avoid the 3 stupids: being around stupid people, going to stupid places, and doing stupid things. These will keep her out of a lot of bad situations. I know that getting drunk is often a big part of the social life on many college campuses, but involves at least one, if not all 3, of the stupids.
2) Awareness/managing unknown contacts at a safe distance. If a low level predator figures out she is on to them and not letting them close enough, they may look for someone else.
3) Unarmed defensive training, preferably based on mixed martial arts. A good MMA school will teach the most pressure-tested techniques for the widest variety of situations in the most efficient manner. The nice thing about unarmed skills is that they are always there, they are never left in the next room, and they are never left behind due to legal or school policy considerations. They can also translate well into improvised weapon skills.
4) To the extent that it may be applicable to her situation, considering both the law in the jurisdiction where the school is located and whatever consequences may exist for violating school policies, a legally carried handgun with appropriate training.
5) Pepper spray. In most places in the US, this will not be an issue either legally or with school policy. Get a spray with an active ingredient rated for at least 2 million Scoville heat units, and a 10% concentration of the active ingredient. A cone-shaped spray pattern is best - it limits the range but maximizes the chances of hitting the eyes at the distances at which attacks take place. Specific recommendations are the Sabre Red Spitfire unit or the ASP Key Defender (also available in a smaller Palm Defender and larger Street Defender).
Regarding lights, the Surefire E2DL and E2DL Ultra are specifically designed with your intended use in mind, and Surefire does build a high quality, durable light. However, the cost of Surefire as compared to other good quality lights, as well as the fact that these lights will go into low mode if turned on within 2 seconds of a previous activation, causes me to hesitate to recommend them. Lately I prefer the FourSevens Quark Tacticals with the XP-G2 emitter (the strobe rate is faster than on Quarks with the XM-L2 emitter), as well as the Klarus XT2C and XT1C. The Quarks are very size efficient, reliable, and can be programmed for one mode with the head loose and another with the head tight. Mine is set for strobe with the head tight and maximum with the head loose, which is ideal for defensive use. The Klarus is a bit larger, but makes both high and strobe instantly available from the tail switch, while preserving access to medium and low. Between the two, I generally prefer the size efficiency and edge in reliability of the Quarks, but find the Klarus user interface to be the best I have ever seen.
