Fair, I hadn’t thought about the timing. But actually I have an idea. What about only having one spy, say something like “They’re here” or “It’s here” but its ambiguous who is being notified. Still have tension but we can assume that the resistance is the one being told, and that the first or found out. Or vice verse and Maz told Poe because apparently they’re best buds (stupid TLJ).
That’s could work well. Han even says when they get to the castle that the First Order ‘isn’t far behind’, so presumably Kylo wouldn’t even need an informant at the castle to know. That would mean that there need only be a Resistance informant in the castle, and I’d choose the lady since she is more integrated into the scene and her somewhat sinister look would sell the ambiguity of her intentions.
I also really like that Maz’s castle hasn’t been infiltrated by the First Order because that makes Han a little less stupid for bringing BB-8 along even when he knows the droid is wanted.