I am glad that you are having such a good time with your dog. There are a couple of things in your post that I would like to comment on.
1. I agree that clear leadership is important for any dog, particularly with a GSD. That does not necessarily mean forceful
leadership. If people are telling you that you are too strict with your dog, you may want to explore that feedback and see if there is anything that you can improve.
2. IMO much of being a good "leader" for your dog is clear communication. Food rewards help with that communication. Many people have the misconception that if you use food, you will always have to use food. This is not true. The food reward is simply to "mark" for the dog what behavior you want them to have. Once they understand, you ween out the food reward. If you watch obedience, Rally, agility, or SchH competitions you will never see food or toys in the competition yet the dogs do some amazing things. I will guarantee you that 99% of the dogs were trained with food or toy. It sounds like you have a very biddable dog and that is great to use that in her training, but don't discount the advantages of other methods as well.
3. Your dog looking to you for permission, I think has more to do with her being a GSD than you being "the boss". I heard many people talk about this behavior from their GSD. Mine is the same way. I am the one that feeds him, plays with him, trains him, takes him for walks... When my husband asks him to do something, he often looks at me to see if he has to.
I had a trainer once tell me this is bad and that it is because I "spoil" him. I don't think so. I think it is because he is biddable and he is used to me being the one to command him. Why SHOULD he listen to someone else?
4. You asked "if she starts to do bad things the only way she will know is if I am firm with her right?" This is only partially true. Yes, she needs to understand boundaries, but she also needs to understand what is the right thing to do. Think about how you train your people to be good sales people. Is it only telling them what they do wrong? You probably have them go to sales training where they teach them right way to do things, you might set up a mentor for them... You said that she is not your employee, but in a way she is. GSDs NEED a job. Her job is to be your dog and to follow the house rules. Why shouldn't she be rewarded for that? How happy do you think your sales people would be if they didn't get paid and you just told them what they did wrong?