In Regency England gentlewomen weren't chaparoned like in Victorian times. It was fine for a single woman and a man to spend some time alone together as long as it wasn't too often. E.g. in P&P no one is bothered when Darcy calls on Elizabeth by herself or when they wind up walking together in the park at Rosings. (Charlotte wonders, rightly enough, if Darcy is falling in love with Elizabeth, but she doesn't see any risks to Elizabeth's reputation and neither does Elizabeth.)