Not sure I would pay too much attention to this although it sounds a bit like Kinesiology which I have seen used on humans.
No idea how it works but it was quite surprising.
I have a pretty open mind about that sort of thing although I wouldn't rely on it 100% unless I had great faith in the person concerned
However, I do agree with you about changing her diet from Bakers asap and feeding her something else - Bakers is awful.
If the new food is suiting her (and you) then I guess it doesn't really matter how you arrived at it.
As has been said though, it is usually trial and error working out what foods suit your dog best
