Spears seems to still be in a situation where her mental health is not the best, and needs the guidance of those in the conservatorship (who also include doctors, lawyers, a judge and therapists) to help her, probably for the rest of her life.
And, the idea that Spears’ father could do anything against the wishes of the others (like hold his daughter captive) without the judge being told, is incredibly unlikely.
It was just in April 2019 that Spears had to use her social media to reassure fans that she was doing what needed to be done for her mental health, after she took time away from the spotlight to stay in a facility which helped her deal with stress after her father suffered a serious string of illnesses.