Can you translate good night my beautiful butterfly translated for a woman in french?

It's a slightly awkward one because in French the gender is dictated by the noun used in the comparison so technically it would be

"Mon beau papillon" (pronounced - maw bow pappy-on with bow as in bow and arrow.

Same whether you were talking to a girl or a boy because the Word "papillon" in French is masculine.

My pretty butterfly would be , "Mon joli papillon".