They definitely don't require a metal nest box. A wood one would be much easier to regulate temperatures and humidity. One for a cockatiel would not be the correct size though, it would need to be somewhat larger. She needs to buy a book on conures which gives the specifics on their size, humidity etc requirements. I also recommend that she gets the birds completely vet checked before starting out on breeding and maybe talk to other breeders to find out what problems may occur and for any other helpful suggestions. I would also suggest making sure she has room for the babies until they have found new homes because once they are past weaning they will need to be removed from their parents cage and may require a lot of space until new homes are found! Many people try breeding birds to make a profit and find that to do it correctly actually takes a lot of money which leaves a person with no profit or very little!!