Hundreds of dogs are sensitive to loud bangs and booms etc.
Its not something that is easy or even possible to cure, as its usually an inborn thing and firmly in the dogs genes.
You don`t say the AGE of this dog though, and the older the dog the harder it will be to try and desensitize the dog to loud bangs.
Also what actually are her reactions when she hears a loud bang?
Does she tremble, cower, hide, seek your reassurance, etc?
You do right to ignore her when she shows alarm at noises and if she is a young dog (under 18 months) she may eventually learn not to react so fearful to bangs, by observing `your` calm reactions to loud bangs etc.
It also may be that the dog has weak nerves, which often accompany dogs that are afraid of loud noises, but that does not apply to all noise sensitive dogs.
It`s hard to give any positive advice without actually being able to see the dog and her body language and to assess her properly, which your behaviourist will be able to do . Sorry can`t help more.
But yes, I did once have a GSD some years ago that was scared of some loud noises and especially if cars back-fired, as they often did in the 1960`s. He would try and hide anywhere he could if a bang upset him. Apart from that he was ok with the world.
GSD owner for 56 years.