For your MC Problem (steadfast drive) of Production, what you can do is first look at the Domain, Concern, and Issue as sources of conflict for her. Then, if you think of an illustration for the problem/drive of Production that fits your understanding of this character, that works! I wouldn't worry so much about how internal or external it seems at the Problem level. "making everything bigger in her head" sounds good to me.
Ooh! This is a perfect question for me as this is the OS (& IC) Symptom/Response in The Princess Bride.
Probability is about chance, likelihood. So as a Symptom the character will really focus in on that likelihood as a problem -- e.g. it's likely that something bad will happen, or it's unlikely I'll get what I want here. And because another word for Symptom is Focus, you'll often see them worried about those chances -- maybe trying to figure out what the chances of something are, "how outnumbered are we going to be in this fight?" and then focusing on the likely outcome "no way, we'll lose for sure" that kind of thing.
Possibility is more concerned about what's possible than what's likely. I think as a Response you would often see it as someone looking for another possibility, going with something that might work.
So working both Symptom & Response together, you get something like... Faced with the likelihood of failure, they look for another possibility. Or, faced with the likelihood of failure, they put their stock in this possible solution.
For me, the scene where an impatient Inigo wants to throw the Man in Black (Westley) a rope is a great one for understanding how it works:
When Inigo is waiting for the Man In Black to climb up, they try to find a way for him to trust Inigo’s lowering of a rope.
INIGO: But I do not think that you will accept my help, since I am only waiting around to kill you.
Driven by that Evaluation, they both see the problem as the likely action that Inigo would take. The Man In Black knows that Inigo will probably just cut the rope again, he’s done it before. But they both try to find a way for him to possibly trust him:
INIGO : You don’t know any way you’ll trust me?
MAN IN BLACK: Nothing comes to mind.
INIGO: I swear on the soul of my father, Domingo Montoya, you will reach the top alive.
MAN IN BLACK: Throw me the rope.
This foreshadows other times Inigo's father offers another possibility, like when Inigo prays for his father to guide his sword.
Now, your MC has a drive of Production which is different from Evaluation (or Westley's drive of Reduction) but I think the Symptom/Response will work similarly.