Crossdressing isn't a hobby (though many just do it for fun) nor is it a disease (though people outside the CD circle may think so).
Crossdressing is a part of a persons personality, a part of who we are, like a sense of humour (or lack of it!). It's the way a person wants to express how they feel inside.
It cannot simply be given up or brushed aside as a passing phase.
CD's go through passing phases of purging, feeling out of touch with the rest of society up to the point of guilt or shame of doing such things. These phases don't last long until the urge of self expressionism comes breezing into our lifes again.
I told my SO (Tamara-GG) of my dressing as early into our relationship as I felt comfortable in doing so, as it is a part of who I am. I decided she had to know the complete me if we were going to spend our lives together. I did this because I love her so much I could not keeps any secrets from her.
If I were asked to give it up or she would leave?
In all honesty I would have to say no. It would be simply impossible for me to disregard a part of myself. Not only that but as I mentioned earlier it is a part of my personality and that personality part of a package of who I am. If there was some way I could stop dressing up, it would probably change my personality and then maybe she may not like who I was.
If it really was a case of either I stop dressing or loose her, then I would stop dressing in front of her but I would continue in secret which would only lead to frustration, again leading to a change in my personality.