What if you had been groomed and then suddenly you are part of a cult? How do you get out?

Good question! For most people there is no "getting out" until a real crisis occurs. Why? Simply because they are 1/ fearful of repercussions; 2/ their willpower has been subverted (that's how they were sucked in to it in the first place).
So: How do you get out? 1/ Run! Simply run away from where the people can influence you. It may mean leaving town and even changing your name, but if you are in fear and you need to get out then - RUN.
2/ Go see a psychologist or a support group. A cult is like an addiction... people feel they NEED the group.... You don't need the group - they need you as a 'patsy' to do work for them. So, where they have built a dependency in you for them, you need to break free of that dependency - you can't do that alone!

Tell family and friends and ask for help

1. Go for the nearest exit.

OR

2. Take over from within.

Smack an FBI agent across the face so they have no choice but to arrest me (If you get the reference you're awesome)