Continuity mistake: In the beginning of the movie when the professor's assistant almost gets her eyes injured, Dr. Merrill has the key to open up the lock on the gate, so she can get out to go to the hospital. Later on in the movie, he says they cannot leave until the morning because he doesn't have the key. So it doesn't make sense that he had it earlier but not later.
Revealing mistake: When Luke tries to ram the gate with his car, a huge piece of spear-point wrought iron falls and impacts the roof of his vehicle. As the others rush to rescue Luke from the car, we can see the wrought-iron spear points flexing and bending, because they are made of rubber.
Answer: She has faith and the courage to face him without fear. After years of bring used and abused, she finally had enough. The only way to conquer your fears is to face them.