How about a gift basket with dorm essentials?
You can start with a shower caddy as the basket, fill it with cheap flip-flops, and other shower essentials -soap, shampoo, conditioner, toothbrush, toothpaste, deodorant, washcloths.... and depending on how much you want to spend, you can branch out to include tylenol, nyquil, cough drops, first aid cream, bandaids, itch cream, etc.
All the things your niece is so used to finding in the medecine cabinet at home, but would not think to buy for herself when going away.
Another idea a friend of mine did for her niece was a handyman kit, with basic tools - hammer, screwdriver, and pliers also removable hooks, double sided tape, masking tape, hangers, over the door shoe holder, push pins, cork board, lysol, windex, sponges, clorox wipes, etc. All things that did not make the "recommended packing list" but all things the girl got tons of use out of.