It kind of does. Or at least, it should. I'm pretty sure that most girls would be angsting about it or having an existential crisis. Not having a past or any memories would normally be kind of a big deal for most people. Meanwhile, Sabrina has barely cared recently, aside from the one or two idle comments. Even before the theory popped up, I don't think it even registered once for her that she might have family or friends out there. Slightly surprised it hasn't been brought up by the others in-story, but it has been a very busy and complicated week.