What Reine said is valid for me too -- "she" isn't a teenage girl, but she's not a competent, confident woman either.
Also, it's creepy that she has all my husband's memories and tends to touch me casually the way my husband would: she doesn't feel the distance between us that I feel, because I'm not the one who looks different. She acts like we're married, but it's weird being married to someone I don't know.
(That aspect doesn't seem like it would come into play if your new relationship meets you in both guy and girl form from almost the beginning, and gets regular doses of both. In that case, my main advice would be to follow your new partner's lead as far as topics of conversation, avoid talking too much about makeup/fashion, and try to project confidence and happiness in both modes as far as possible.)
