If it is fact - AND HE DIDN'T GO LOOKING FOR BB FS then we should all know. If this guys goes out looking for BB FS and gets it, then shut the hell up and keep it to yourself, you got what you wanted, what you went searching for, so don't bring down the girl for giving you what you were hunting for - there is a reason why you picked her, and odds are others know about her BB FS reputation and can make the informed choice.
If he didn't go looking for this, and it was offered, then she may be a 'closet' BB FS provider. Someone we all need to know about so that we can make an informed choice. The only other exception I could make to this would be if the client really believed (whether correctly or not) that he had an unique connection with the SP and that this was not proivded to other clients. In that circumstance, it would fall into the keep it to yourself category.
That, my dear GBM is what it is all about, what PERB is here for. Sharing information and about making informed choices.
If the guy is lying, off with his balls! If he is telling the truth, and did not go looking for it, or pushed for it, then the girl should not be surprized / offended that it gets out.