This essay is the best thing I have ever read on this site. The most important task is to maintain or rebuild a loving parent/child relationship. Don’t argue about gender…they are under the influence of a cult and are not thinking clearly.
Get your teen outside in nature, take a trip, exercise together, at start a hobby together that you both find fun. You need it too.
Then when the bridge of love and trust is re-established, you can slyly start planting seeds of critical thinking that will help them regain their sense of self.