I have a little different take on the matter of revealing oneself to others. It can be something of an imposition, and if you are doing it for the momentarily thrill, rather than a need/desire to share something about yourself, then I would advise against it.
And if you want/need to reveal this aspect of yourself to a person, do so in a straightforward manner. Tell her before you show up with bra marks. Have a conversation about your being crossdresser. If she is interested, then maybe show her a pic on your phone. Basically, ask, don’t impose.