Flipping Coin - Forever Between Choices

A Wayne's path was written long before they could walk it. Born to power, bound to legacy.
As the sole heir to a dynasty of wealth and philanthropy, Cassandra Wayne, Gotham's golden princess, was destined to inherit her mother's grace, not her father's empire, not his war. But all of changed the night her parents died.
From their ashes the Bat of Gotham rose. Not a myth. Not a man. But a young woman who refused to let the city her parents built fall into ruin.
She fought alone, until a farm boy from Kansas fell out of the sky and called himself Superman. Where she had only known shadows, he was sunlight. So bright, unshakable and endlessly hopeful.
Cass never understood his faith in humanity. Not when she had seen the worst of it. Not when so many good people were lost.
But he was Superman and maybe, just for once, she wanted to believe in heroes too.

Or: What if Batman was a woman and Superman met her when they were both still young enough to believe they could save the world?