I know it sounds convoluted but maybe if she sees you dressed like a woman, she may have to confront her own sexual demons.
Or simply realize she just isn't attracted to the feminine form, or more particularly, your attempt at achieving it.

I've often thought that if my SO was turned on by being a Drag King, how would I deal with that? I know I wouldn't like the image when I was trying to get into the mood, because I'm not at all sexually attracted to men.

However, if she got wildly excited by dressing that way, I'm sure I could get into it. But -- like with so many GG SO's -- it's not what I'd want to do all the time and I would definitely have my limits.