Is my dog protective?

She is an all-muscle German Shepherd/English Setter mix. She's six years old now and has been leash aggressive her whole life. We've been to 2 group classes, a one-on-one with a trainer at our house, and even an 8 week long boot camp. None have been able to fix this, and we just don't have the money to throw away on something that won't work. We talked to a dog trainer about it and he said she could be protective of me (I'm the dog walker of the family) on walks. She loves people on walks. She smiles and wags her tail and tries to go up to anyone she sees. If she sees a dog she lunges and jumps forward as much as the leash lets her, barking loudly and aggressively. She doesn't growl or anything. I turn her away and walk in the other direction and she marks her territory right away, as if telling the dog not to come near us. She whines a little and always turns around to look for the dog. Is she "protecting" me from other dogs? This got a little better when we got our other dog, but they don't play or anything, so I'm her playmate. We used to have a black lab puppy over that she loved, but he moved away last year. Our neighbor has a mini poodle that used to be friends with her, but it hasn't been over in a long time and I'm afraid she'll hurt it, even though she was really nice and gentle when she came over.