A long shot, but your dog may be inherently anxious. If that's the case, slowing down & backing off can help enormously. For example, when you praise/reward, do so calmly and briefly. Do one minute of training and stop. If your pup does get anxious for any reason, calmly & briefly soothe her. If that doesn't help, put some space between you and ignore her for a while. Remain calm, as well. I know it can be difficult but makes a difference.
I had a bc years ago, Shoshone. She had been badly abused/neglected and had been in a good foster home for a while before we got her. Her anxiety was intense, she was afraid of everything. She'd leave the room when we had friends over, hated getting into the car, etc.
Got my vet to prescribe prozac for her, which did nothing. Asked the vet if there was any other medication that might work. He prescribed clomiprimine. A few weeks after starting clomiprimine a dog-loving friend of mine dropped by. Friend got down on the floor to say hi to Shoshone. I went into the kitchen to get something or other. When I got back to the living room, Shoshone was on my friend's lap, soaking up some love.
Your girl may not respond to medication, but if she were mine I'd give it a try. I think the medication was inexpensive, but this was at least 15 yrs ago. In any case, please let us know how it goes for you and Luna.
Ruth