Fear not! I shall answer your questions with absolutely no logic or authority but my own
What happens with two Zeldas? *giggles immaturely* nudge nudge, wink wink
Since the current monarch of Hyrule would be the descendent of this original Zelda (or at the very least be descended from her sibling) then the AoL Zelda would have a legitimate claim to the throne. I doubt the standing monarch would like that though. *She was cast out into the crumbling kingdom of Lorule and renamed Hilda, there she waited many decades until she had her revenge on her cold blooded sister*
Link, by saving Princess Zelda might have started a civil war. *points to hyrule warriors with as much authority as she can muster*
Nintendo flesh this out please! *Nintendo ninshmendo! We just did*