First of all, forget about a waiver. It won't be approved. That means you must provide the evidence of having met. Boarding passes, receipts, documents showing you were inside the US SHOULD suffice. However, in this case, I would absolutely get affidavits from a few people testifying that you actually met (with dates). If you have videos of both of you, I would also take a couple screen shots showing you together.
Concentrate on proving you were in the US.