She pulls her blanket back up around herself and begins thinking. What does she care about most strongly? Right now, the thing she's most focused on is getting magic, but she doesn't think it's quite accurate to say that she cares about it so much as she is very interested in it. What was she thinking about before Kyubey showed up? Looking back... the cold is terrible. True, but not the sort of thing she wants to waste a wish on. Novels and games, no, those are short-term fun but not much more than that. Living on her own and never having to deal with her parents again? Much closer, probably something that she can muster a decent amount of feeling about, but... she has potentially forever to do that. As much as Kyubey might expect her to get killed within a couple years, she knows better than that. If nothing else, she can just wish to be unable to die. Or... no, that's a stupid way to do it. Not when both of the causes of death Kyubey mentioned are dependent on loss of magic. In fact, now that she thinks about it, wouldn't the obvious wish just be for unlimited magic?
Wait a minute. No. She's thinking about this all wrong. Why, if magical girls exist and can do all these things, hasn't she heard of them? Witches might be able to hide themselves from normal people, but Kyubey didn't mention magical girls being able to do that. Which means there's some sort of extra filter here that she's not thinking about.
Turning back to Kyubey, she asks, So why haven't we taken over the world yet? Not, like, as a group, but if magical girls are so hard to kill, why aren't there any countries ruled by unaging god-empresses? Girls who wished to be the untopplable rulers of the world, and never got toppled? Girls who wished that nobody else be able to take them down, even by wishing for it? Because those things haven't obviously happened, but nothing you've told me has pointed towards any sort of filter either to prevent those things from happening or to prevent people from noticing if they did happen.