Spays - be careful. If she's resorted to biting you I'd be keeping an ever closer eye on her. I've checked god knows how many spay sites and can't remember any trying to bite me. Usually they're sore but not so sore that biting should occur. I'd be concerned about that, sounds like she's not gone to plan to me.
It's always best to look at your dog in the way you would a kid. You want to teach them about the world and then hope they do the right things from what they've learned and experienced, being a good role model etc, rather than being someone who only gets them to do what you want them to do - regardless of how they feel about things - out of fear. A dog that 'rules' a person is just a dog that hasn't been raised right in the same way that a little shit of a teenager hasn't. You want to have a good relationship and in truth that starts before you'll usually even get the dog, but even then, most people start the whole process making mistake after mistake and then spending the following months and years either hoping to fix the things that are wrong (which they usually do incorrectly and make it worse) or they don't even try and just accept the bad things as part of the dog. These things can be worked on and rectified and it doesn't take a beating to do it either.
Consistency more than anything is key. If the dog knows what things mean life should be easier. If lots of effort is put in to make things positive for the dog, life should be a lot easier. But we mess up so much, right down to even the words we use. How many people do you know that say about fifteen words when they want their dog to sit, or shove its bum down? Not only is one word enough, you don't need any words or to touch the dog at all if you understand more how dogs work.
You can lead and instil confidence without having to be any kind of a bully, and what many people don't realise is that the dog only understands so much of what we want to get across to them but that's more so on us (although they pick up on and learn a hell of a lot more than we realise through their off-the-charts ability to read body language, especially). My last dog would do anything I asked her to do, not because she was fearful but, much like us, she was happy to do things when she got something out of it. Think about it: would you sit if someone said sit at you fifteen times when there's no reason for you to do so? Or before you've even learned what sit even means? Would you if they shoved you to the floor to make you sit? Or how about if you didn't sit when asked and you received a beating until you did so? Or would you be more likely to sit if, when you did sit, you were given something you saw as good? We all should know this yet still many of us do the former techniques before the latter. Why?
The principals of behaviour are very similar but for some reason we expect people to treat us a certain way, and many of us will treat other people a certain way, but we look at animals and recede back to a caveman way of being. And that's largely because we think it's an animal and it won't understand. The weak link in the chain here is us and our lack of understanding and unwillingness to learn about them and how best to raise them and treat them and interact with them.
Much of what has just been said in the last few posts goes back to the same thing that I mentioned previously about the wolf studies. The dog world was based on that and it STILL hasn't filtered down to everyone that all of that foundational 'knowledge' was incorrect. Cesar Millan, a chief exponent of such outdated methods, got to be who he is because some rich prick liked his story as a migrant and gave him a show off the back of pretty much nothing. He hadn't studied, he'd just learned off what I think was his grandad. He then got a show that reached tens of millions of people, the world over, and set any progress right the way back. And still there are new guys coming through doing all the wrong things, getting thousands and thousands of people to watch and copy them, and all whilst doing things that can make things worse - and dangerous!
The older generations still think of this and the existing knowledge at the time and wouldn't have even heard of anything else since, I'm sure. And as alluded to above, there are also now loads of people out there spreading more info because they did a shit short course or two who should not be passing on 'wisdom' because they have none. It's why things have always been and will continue to be slow moving in terms of the dog world and behaviour.
A mechanic can sort your car, a dentist can sort your teeth and so on, yet we trust clueless people to tell us how to 'fix' our dogs. The experts for this do exist and they can be easily found. (By the way, the comment about the vet isn't surprising, vets aren't experts in behaviour until they have added those qualifications themselves as well. Many of the older style ones will likely act like the one mentioned because they haven't sufficiently studied it).
When I was doing my studies I remember reading about some of the studies they conducted in the 50's and 60's etc. Some of it was truly frightening but we did learn what dogs can and cannot do. Funnily enough one such study involved whacking the dogs as a punishment and it revealed that the dogs don't have the ability to associate between incident and punishment after more than a few seconds, so you're beating them and they don't know why. You literally teach them to be afraid of you rather than to correct any bad behaviour. It only works as a punishment if it's right in the moment (much like us touching an electrified fence or a hot fire surround or something), and guess what, they still see you delivering the punishment so they still learn to be afraid of you. So if you come home and find your dog has done something, no amount of shouting or hitting will have any effect other than a negative one in terms of your relationship with one another. A classic example of that is coming home to the dog and finding it has shit everywhere, so you smack it, or rub its face in it. That'll teach it, huh! What you're likely to get is either a dog that shits more so because it's afraid of your return, or starts chewing as a way to relieve the anxious stress, or one that removes the evidence by eating it. And so on and so on...