How about a greeting card that says welcome to your new home and put the membership card in there. She'll have to figure it out a bit. If you have the membership card by May you can give it to her at the graduation. She'll just think it's a graduation card.
Do re-sale have a membership card that can be printed from the website ? I was under the impression that is how they are disallowing access to member lounges and discounts by not providing membership cards.