Just the statement that you made saying, "at first, she was uncomfortable with it", tells me that you are heading down a dead end road. You love her? you want her? you better let her wear the panties and you be the guy.
If the situation were different and she actually loved the fact that you liked to play dress-up and be the girl, it could very well work, but women who only tolerate your dressing because they care about you soon grow tired of "the other woman".
A woman needs to feel that she is the only woman, that she is adored and that you only desire her.
I'm just saying.... so be true to yourself, but be realistic about it too.