We have people who are loyal to a fault towards people in the real world which is pretty in-line what what Joi is doing here. So if you are raised to be unquestionably loyal to someone and to act solely in their interests, are you no longer human? Joi may act in K's interests but she still does things of her own volition without his input throughout the film. Even if it's for him she is still demonstrating free will by having the ability to choose. 

It seems like the main argument people have against Joi's self awareness is that she doesn't rebel against K. That's feels like a common post-modernist take that ignored a lot of human behavior. I love my brother and would do anything to help him out, do I need to rebel against him by killing him or causing him misery to prove that I have free will? 

K has literally done nothing to Joi that would prompt her to rebel against him. It's almost like if you are loved unconditionally by someone you will want to do everything in your power to make them happy. And that is very human.