The gift that'll keep on giving...
Good bro, you are...
I'd say:
Macbook, refurb, black or white.
Unless you know she's devoted to interests in video editing / hard core graphic manipulation, etc. anything above this would be overkill, and waste of $.
I say refurb, b/c (don't know how deep your parents pockets are) but the reduced price may hook them to your suggestion over say a Gap gift cert. And based on what I've reviewed there's far more reasons to go refurb than to not to.
Whatever ram comes with it will be good for her (unless devoted to intensive interests listed above)
~misc
-USB 2 button mouse
-blank DVD-r's and CD-r's
-Protective notebook carrying case
-iWork - can produce documents in the expected M$Word format, but so nice to use, and does dandy presentations too
-something like OS X - The Missing Manual
http://www.amazon.com/Mac-OS-Tiger-Missing-Manual/dp/0596009410
-SECURITY CABLE for the Mac -find one with good reviews, don't cheap on this
That's my two cents; as for HD add-on, I think it'd be safe to wait until that need is crucial rather than getting one now; unless she loads it up with movie-files, most of what a first year college student will be up to wouldn't fill up the HD too soon... that goes w/extra ram too.
nf