If USB port availability is one of her main concerns, I would suggest staying away from the MacBook unless she is okay with dealing with dongles. That being said, as a college student myself, I rarely need the extra ports, and when I do, I have a dongle that gives me 3 extra USB ports. It's not very much of a hassle, in my opinion.
With respect to storage and battery, the MacBook starts at 256GB standard while the Air starts at 128GB. Bumping the Air to 256GB results in both devices being about the same price (especially if you order from B&H, which has the MacBook currently discounted to $1199). Battery wise, the Air is better, giving 12 hours of battery life compared to the MacBook's 11.
One important thing to consider it the display. The MacBook has a much better display due to its higher pixel density and much more modern display technology that results in much better color reproduction.
If I were to recommend between the two, I would most definitely recommend the 12" Retina MacBook (I know the beginning of my post didn't make it seem that way, my bad
![Stick Out Tongue :p :p](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
).