One thing to keep in mind - while many of the replies here have addressed the courtesy issue of the situation, many of them have come from US based SMs who are bound by US hiring laws. Many of the precautions that we take are as a result of these laws. While the courtesy aspects remain, we must remember that kiwitechgirl is not based in the US and there may be cultural and legal variances between countries when it comes to hiring practices.
I am NOT a lawyer. All subsequent advice is based on knowledge I've accumulated from working as a recruiter and in real estate, both of which deal with employment and other contracts on a regular basis.
In the US, it wouldn't matter if the job was paid or not, kiwitechgirl would be opening herself up to a defamation suit and possibly an antitrust suit if the company name were invoked in any way in the course of her correspondence. I don't know where the laws stand regarding contract law, antitrust and defamation in NZ, though.
Just to be on the safe side, here's what I would suggest for next time. Do not offer any advice or opinions before a hiring decision is made. If someone enquires after the hiring process is finished, you can feel free to offer suggestions based on your experience of things you did to ease the task of working with the person that were successful in controlling their behavior. Other than that, unfortunately, silence is the best policy. The ONLY exception to this is when the applicant has given your name as a reference, and even then, it is the safest bet to only answer objective, yes/no questions. ("Did they arrive on time to rehearsals?" - OK to answer. "How was their attendance record?" - Not OK.)