This is a good piece of advice. At the moment I teach one business woman on-to-one in her factory. She even gets me more students. Chinese adults prefer native speakers because we teach them the English they need to know to use the language. At first I recommended to her a Chinese teacher, she fired him and insisted that I teach her. I guess in China, some people need English to actually use it and not for testing. I have her reading, speaking, and writing good English now.
I just turned her down recently for a free trip to Bali with her and her family. Call me stupid, but I can't allow myself to live off other people. I was tempted though.....

Really good news, one-to-one can be most rewarding and not only financially.

You have to do or not do what you feel comfortable with; but you can upset them by rejecting such kind offers. The way I read it, is that she was showing you that she respects you, respects you enough to give you a bonus. I would have accepted the trip to Bali, unless I believed her to have been unstable, but I take it that this was not the case.