If I were answering this question as if I were Serena Joy herself, remember to keep it in first person, and keep in mind that she was a true believer, and one who thought that the society that they were living in was ideal, and the best way for things to be. At least that's what we THINK she thought; we don't get inside her head, but her past as a religious devout and activist for virtue can lead us to infer that. So, here is what she might respond with:
Even though fear is a negative virtue and an unfortunate one that must be used occasionally, it is incredibly effective in helping people to understand and learn what is best for them. People are ignorant, and they fight others who only want what is best. Because they won't listen to reason, we must keep them in check, and fear can work to their advantage, pushing them towards conversion and reform. Once they have lived the lifestyle for long enough, even if it was prompted by fear, they will eventually realize that it is the best way, and their hearts will change themselves.
People will find numerous ways to rebel in a constricting society. It is something that they do to push the limit and to test their own understanding of things. For example, they will find small ways, here and there, to break rules and let their individuality be shown. Their rebellion is unfortunate, and rather common, and that is where manipulation comes in. We can use our power to try to manipulate them into obedience. If not, they might damage themselves, and those around them. Rebellion, they think, is a way to exert one's will in a world where they feel powerless; it will take quite a bit of convincing to help them to understand that it only further limits their freedom and is dangerous.
So, try that for a response for her perspective, and I hope that you do well. Good luck!