[ She's drawing parallels. Vriska can't help but find similarities between her life then and her life right now. In both scenarios, she is going to choose to do extremely shitty things. And in both scenarios, as awful as she's going to be, all she truly wants is to help.

But for now she just raises her eyebrows at him. ]

Of course it's an option. You can do whatever you want. I don't actually know what would happen if you failed to participate, or even tried to leave the Sirens. But that is something you could choose to do.