"Are you an actress?"
Translation:Actores dych chi?
'dych chi'n actores?' is an acceptable translation and has been added now, thanks for the comment.
It does have a slightly different meaning to 'Actores dych chi?' which has the emphasis on the word 'actores' and is asking if the person is an actress or some other profession. The sentence you suggested has the emphasis on 'you' and would be generally 'are YOU an actress' or 'are you (really) an actress'.