That is surprising that she could call. I went to NSI 3 last year with my wife. I would recommend it if it is not a major financial cost for you. We had free miles for the plane ticket and stayed at a cheaper hotel away from base. We treated it more like a quick getaway for the two of us with the bonus of seeing DS at the end. If we would have paid alot more money, it would not have been worth it to be honest.
One recommendation I do have is try and get a plane ticket that has the same return flight as your new Midn. That way you can hang out at the airport with your Midn. We did that and enjoyed it alot more that the graduation. Didn't sit next to him on the plane, but no biggie.