She was never asked about it because it was a stupid fringe theory no one was taking seriously. Once Obama was elected and right wingers including Trump ran with it it became a big deal.
Trump was asked about Duke being being endorsed by the most prominent white supremacist in the country is kind of a big deal. But Trump could've neutralized the issue just by openly denouncing him like any normal candidate would.
It is not a big deal to me. It is obvious that they would like candidate that wants to deport 11m criminals, build a wall and enforce the Law. How is it strange/big deal?
Correlation does not imply causation — period.
Then why doesn't Trump denounce him?