The key phrases are "never really tamed down" and "Fine with other cats but wary with us." That sounds strongly like a feral cat. How old was she when you found her? If she was much over 8 weeks, you missed the window of opportunity. She would naturally be fine with the other cats because that's the society she knew from the start. She never got to know people. You did what you could for her, but it seems she was more comfortable out doors. Sounds like maybe a more dominant cat chased her out of the area. It's rough. I've had a few that I wish I could socialise and find a home for, but it's just too late for them and I have to leave them outdoors because that's where they're most comfortable.
