Engine, since it is not advisable at this point to reveal that you know about her affair, is there any other excuse you could use to request that she switch to another PT? maybe "I have heard great recommendations about so-and-so as a personal trainer, and he/she charges a lot less per hr than your current PT" or something like that? of couse she will object to the change, but you can put her in a position of having to make excuses for why she doesn't want to do so.
