Just keep the lines of communication open. My wife and I are splitting, but we are staying friends. She tried to accept the new me as a lover/spouse, but could not. She too, "married a man" and couldn't stay married to a woman. We make better friends than we ever did as spouses. She helped me learn makeup, and helped me get clothing. As long as you communicate with her, not just about your transition, but as the person you are and your life together, you can possibly maintain a friendship.