I wouldn't call it "regret" exactly but in a recent interview J.K. Rowling admits to selfish motives regarding the beloved romance between 2/3rds of our favorite trio.
From the hybable article on the matter:
“I wrote the Hermione/Ron relationship as a form of wish fulfillment. That’s how it was conceived, really. For reasons that have very little to do with literature and far more to do with me clinging to the plot as I first imagined ... Read More