Watching the classic "All about Eve" I stumbled upon this sentence by Margo Channing:
Please don't play governess, Karen. I haven't your unyielding good taste. I wish I could have gone to Radcliffe too, but father wouldn't hear of it. He needed help behind the notions counter. I'm being rude now, aren't I? Or should I say, ain't I? [From Wikiquote]
I can't fully understand what she's saying with Or should I say, ain't I?
To me "aren't" and "ain't" have the same meaning (in that sentence). Is "ain't" more elegant or the other way around? Is she asking which word to use, pretending she doesn't even know English?
I hope the quotation is all you need to understand the sentence.