I think best approach would be for your fiance to tell his mother and show the pics to her too and she can talk to the daughter. I would feel extremely odd if my brother would talk to me about certain things... even when i am doing it wrong.. clothes.. short clothes.. umm NO... If he diapprove of the way I dress up I would prefer my mom talk to me rather than him telling me he saw my pics in sleevless clothes and hugging guys.. Not that I do that .... but I am just sayin.