With sour crop, her breath would smell like sourdough bread starter and you'd likely find air 'you'd be able to hear it squishing' when checking her crop. Yeast may be visible as a white growth in the mouth/throat and/or around the vent.
Wait and check her crop in the morning to see if it is empty before taking any action. Sour crop tends to put them off eating, so do monitor to see if she is getting to the feeder or grazing. Out of all my birds, my Silkie has the oddest crop. It's small and usually so full that it's rock hard. When she was a chick, I thought she was impacted for sure, but that's just how her crop is. Even today, she's brooding and it's so full that I could see the pellet shapes through her skin.
It may be that she has a piece of grit that's not sitting quite right, causing her to want to make a few adjustments.