my Sumatra's are pretty predictable. Once they start acting the slightest bit broody it is only a matter of 4 or 5 days before they go broody. It doesn't matter if I take their eggs and give them golfballs, or if they have 13 of their own eggs. They just do it.
But Sumatra's haven't been messed with to deter broodiness. Most large foul have been. It sounds to me like your girl may be thinking about it. But hatchery breeds have had the instinct to brood bred out of them. But it still can happen. Broodiness is instinctual. Your girl may, but you are doing all you can do to encourage it.
Of all of my large breeds I've never had a broody. Although a few have toyed with the idea. I currently have a barnyard mix, I think she is a Jersey giant and RIR mix toying with the idea. Yet this year i have already broken 4 broody Sumatra's, had 2 break themselves, and have 4 broody's on eggs.