I have one that does something similar, his reactions seem to be fear based. Once he is introduced correctly, he's fine. I am just having to deal with his 'A Good Offense is a Best Defense' way of thinking.
The distractions with food and toys are a good way to go with this. At least, it has been for my Coulter (not a GSD, but sounds similar to the dog reactivity your Lara is dealing with). I have worked miracles with a pocketfull of cheap catfood. lol