In ‘text book’ abuse it begins with emotional, and while it moves to intellectual, there is a deliberate segregating of the victim from friends and family to insure that there is no one in his or her life but the Abuser; the Abuser and his/her friends and family. The Abuser and his/her life fills the victim.
Without the Abuser, the Victim has no one.
Gerta had to cut Rick off from his family and friends so that he would have no one but her.
Carrying him thousands of miles away to her country and not allowing him (not paying for his ticket) to return home was part of her control.
Another part was making it virtually impossible for him to stay in touch with his friends.