I can understand your apprehension, and I recently found myself in that position, but I just knew it would be better for all, and particularly so for Daisy, if I left. Leaving your dog with a (virtual) stranger, however highly recommended, takes a huge leap of faith, so I do know how you feel. But I really do think it is the best way - especially for the dog. I know that the groomer would have a really hard time if I hung around. In fact, I think it would be unfair to expect her to do a good job with the owner watching every move.
I tried to turn it into a positive and spent the next 3 hours, doggy free, and doing something I really wanted to do. That way it takes your mind off it (a bit!) and time flies by.
But do make sure your groomer comes recommended by people who have used her/him, and that you are more comfortable (I won't say "happy"!) to leave your dog there.
Good luck.
Kay and Daisy