here's a different train of thought...
I doubt any song is adequately going to convey proper sentiments or speak to ones soul. Id choose something uplifting that you and her can dance too easily. Perhaps something by someone she likes, or something that touches some prior event you both enjoyed. Its a big day for the both of you, maybe something out of both of your past remembrances would suffice. It isnt necessary to shoot for perfect here . Merely pleasant.