I'm a (used to be VERY serious) pro married to a very casual amateur. It works as longs as I don't pressure him to dance "correctly" or get annoyed that I can't really show my stuff or do more than a few steps a dance.
Usually it works but sometimes I do get frustrated or he gets nervous, feeling pressure... so we just have to back off and remember it's for fun! No way he's going to rev up to where I'm at, so I have to adjust to his. If you can't do that, I don't think it will work.
Luckily he was always fine with me dancing and partnering with other people. In fact I think it helped that he did some ballroom, because he understood why I had to practice so much, and that partners didn't have to be romantically involved.
So if you can let go of formal ballroom in a social situation, and she can accept your ballroom self where you need to express it, you guys should do fine!
(married 3 years, together 5)