Unfortunately for you I'd say, in my experience, trans women probably aren't any more likely to be okay with that than any other women. For different reasons usually, but still.
Chances are if you bring it up to her, she'll really just not want to have anything to do with it. But then you've got the chance that it's something that'd nag at her a lot afterwards, so it might not be worth bringing up. I dunno. Depends on how much you like to be truthful but it will very likely not go well, even if it doesn't go badly.
To be honest, a good relationship is better than a kink anyway, despite what hormones might sometimes tell you. Maybe leave things be for a while and figure out what your priorities are. Tell her then if you still want to.