oopsylon says:
... The questions I was hoping to ask ...
Yeah, those two are the only ones that are really possible.
oopsylon says:
... not immune to persuasion ...
Yes, this could give you a route to
Persuade an NPC. That is feasible. The risk of rolling is that you might Miss, the upside is that you get to introduce something into the fiction that will definitely count as leverage for triggering Persuade.
Roll
Figure Someone Out and then we can see what you learn. On a success, feel free to tell us what you discover that can serve as leverage for however you wish to Persuade her.
oopsylon says:
... is there a reason low-status NPCs can’t incur Debts? ...
She is a
no status NPC, she does not know about the supernatural world and therefore does no participate in the Debts mechanic per the rules.
oopsylon says:
... they could still owe someone a favour ...
Favours are not Debts. Debts are enforceable, both by the mechanics and by everyone in the world who is aware of that whole part of reality.
You could possible get her to owe you a favour, but that would be a purely fictional thing and you would need to talk to her about it to get anything from it. It could be on the same scale as a Debt, but does not have the backing as a currency that Debts do.
If we want to get her involved in the Debts system, then we will turn her into a Status-0 NPC and find that she
does know something of your world. This is fine, it makes sense for a grizzled old sergeant to have seen things that are hard to explain, but she is possibly in denial about.
This is sounding more and more interesting, so if you get a Success and choose to invoke Debts, we will do that, you would need to remind her of the reality of the world, and that might have ongoing consequences. If you can get her owing you a Debt you could leverage that to get in to see your friend without needing to roll Persuade, though that would require you doing something for her first, you can tell us what she needs if you have ideas.