What I would actually do is give her the $100 as her gradtuation gift and then purchase the remaining $200 in giftcards of $50 each and then send them to her every 3 months during her 1st year of college!!!!
That way she can buy herself something pretty or go out to dinner or buy replacment books or whatever as she needs them. You could get the AMEX gift cards which she can use just about anywhere.
Not only will she appreciate the money, but she'll appreciate getting a card with some well wishes and maybe some pictures of you guys out of the blue. Will help her feel connected when she is alone at school.