Today is St. Patrick’s Day, a day where people with–and without–Irish heritage take time to drink green beer and shamrock shakes.

Right. Go on with your bad selves and all.
So anyway, speaking of self-identification, I’ve been revising my Regency-set historical, and my heroine is a vicar’s daughter, raised in a small village, who ends up marrying a marquess.
Imagine how off-kilter one would feel entering into the ton; not only would you not speak in the same accent, you wouldn’t know the families, nor the customs, nor even how to behave during a dance (I do presume she knows how to dance in the first place). It’d be like being a brand-new entrant to a family that had known each other forever, had their own in-jokes, vernacular, and habits. She has to ask herself if she wants to continue to belong to this world, given she feels so out of place and knows her husband has married far beneath him.
Of course you know how it ends, but meanwhile–what do you do when encountering those incredibly awkward situations? What should my snappish, smart heroine do?