Also, my reading of the rules is that if she had merely said she was going over to advise them based on her US experience at NERAX, she probably would have been OK. (Advise and trouble-shooting are apparently valid business reasons to be considered a non-Visa national.)
Except of course that if you run up against an immigration officer who is a CAMRA member (and as there are 150,000 members the chances are that at least one is an immigration officer) they'll know that CAMRA has been holding National Beer Festivals ever since 1975 and so are much more likely to be providing advice to others on how to run one than needing it themselves.