Been there. Keep at it. Sounds like she was a good boss and you liked her. I suggest writing a card stating what you wanted to say and couldn’t. Be humorous as appropriate between you two. She’ll appreciate it and you’ll feel better. Keep trying different speech therapies until one clicks for you. It is very personal. Get some psychological therapy, too. I suggest cognitive behavioral therapy. Very practical and results oriented. Be sure to assess your self image. It is certainly distorted. It is for all stutterers.