I'd say there's a few factors. What course is she looking at? Is it one that will require intense computer use, or use of intense programs (video editing, some science programs, any assistive software). If she's just needing a standard laptop with office software then a MacBook Air is a great computer!
What university will she be attending (all going well) and will she have easy access to an apple store, or a John Lewis or both?
Apple Care is good, and can also be purchased within 12 months to 'spread the cost' a bit. You'd need to see if JL can also be that flexible. Also what the JL warranty covers, compared to AppleCare.
Apple discount is very good, and they usually also have a decent 'new academic year' offer of an apple store gift card, or free headphones or something similar when you buy a new mac or iPad for university. Those offers usually come out end of July/August so hold your horses a little.
She will likely get access to Office for free through her university, but I'd say get the (also free) iWork's suite, the programs are better (IMO) and work well on the Air, you can also open and save documents as windows files (if her uni runs windows).
I have a 5 year old MacBook Air and have had zero issues with it, although now it needs a new battery but that's fairly standard. I will be upgrading to a MacBook Pro in September as I need to run some more processor heavy programs and my Air just can't cope.