Well, I mean, fire's red, and fire is the appropriate pairing for a black dress shirt.
I'd be pretty firm about the white shirt. You know your relationship, and you know the degree of disagreement it's worth -- it's certainly not a big deal.
Matching one's date is kinda bad, and crimson ties don't look very good. Black long tie would be better -- not only is it more tasteful not to match, it also directs more attention back to her. Heck, the biggest criticism I'd have for black suit, white shirt, black tie for an evening event is that it's a little too Hollywood -- not so much a problem in your scenario. That said, this is very much her event.
lolololololol I laughed so hard at this