Well, my boyfriend actually had the same dilemma a few months ago! He and I had been dating for awhile, but I had no idea how submissive he really was. My advice would be to first, talk to her. You can tell her that you really like being bossed around, or, whatever. The way my guy did it was to say "I love it when you're a bitch in bed".... and go slowly into it... have her read some erotic stories about the stuff, if you're open to it (but not REALLY scary ones)... especially femdom stories. Maybe buy her a pair of handcuffs or something? Whatever. Just as long as you go slowly you won't absolutely freak her out.