If you are going to attempt to "alter" her vision in any way, I would recommend giving it a run before the wedding. The idea to buy the pure white tie and show her that, in fact, it does not look that good is a solid endeavor. The white (or off-white) vest on the groom in combination with white shirt and light tie is pretty popular currently. I have seen it at the past two weddings I have attended. If you mix up the patterns and tones, you can probably make it look kinda cool. For example, white shirt and cream/silver tie. I am a big fan of this tie previously recommended: I think the white PS is the least of your worries in the ensemble since it will be somewhat offset by the dark jacket.