There is only one species of reef safe banner fish, the others arent (as your friend found out) and its really hard to tell the difference between the two.
If your tank is it enough then there's no problem with getting one that doesn't eat frozen but, it doesn't hurt if it eats frozen as well just in case. IME a 75g was large enough for one that did not eat frozen.
I understood from previous threads here that butterfly fish are very difficult to take care of and would be best to leave in the ocean. I had many problems with hennies & just gave up. Is her tank big enough for bannerfish or Heniochus?