Is wearing a sheer top in a casino offensive? Adults only please. 10 pts. best answer?

So my friend asked me this question and I told him I'm not good with fashion so I have decided to ask you.

He wants to take his wife to a casino where there are only adults. He wants to surprise her with a weekend trip.

The question: Is it appropriate for her to wear a sheer top? He is going to buy her a blouse of top that is black and sheer. He knows she would wear it if he asks her to, but he was concerned about too much exposure. Should she wear it with a camisole under it or just a black bra? Should she wear it without a bra? Should she wear a strapless bra? I'm not sure how tight of a blouse he is planning on getting, but I figured if it were loose fitting and perhaps with lace she could get away without wearing a bra at all. I told him to look into getting pasties to wear under the blouse. lol. Not sure if he would. He is trying to get the "sexy / slightly slutty" look without dipping into the "whore" look. He said he wanted some guys to take a double-take, but not try to buy her for the night. How would you feel if you saw a pretty girl who carried herself very well and lady-like wearing a top the was see-through? Would you be offended? What if the top was only see-through from certain points of view? Any help on this is appreciated. Any ideas on this is also welcomed. Thank you.