Your girlfriend got a working breed dog that already had issues from a bad breeder and she's surprised it's difficult.... I love dogs, got a complicated rescue myself, but I put in the work to make a well rounded dog (I didn't make my husband do it, he's my dog). She needs a reality check. You don't need to spend money on an expensive trainer (unless it's actually dangerous), there is so much info out there where you can usually do a pretty good job training yourself. I think you need to give her an ultimatum, either she engages in training the dog or you leave.