And now she comes when she's called, she has even come off chasing a squirrel to my whistle. But she still hesitates and runs on a stride or two, apparently just to show her independence.
But she just turned 3, and I'm starting to see a real improvement in her general obedience!
Exactly! The only way to ever get precision off leash with an opinionated dog!
There are two things, IMHO, that all dogs need to be 100% on to be safe loose. The first is 'COME', but the often better solution depending on the circumstance is 'DOWN'. To be able to know they will just drop and ~stay~ where they are till you get to them is the only safe way out of a situation where they are on the other side of a road.
I only used it for a real short period with my female, to teach 'come' and 'down' and that was it. Once she knew the expectation, she didn't question again. I can get her back from anything now.
I did a lot more work with my male lab, but I was hunting and showing him, and he was not only more strong willed, be had more complex work to do.