Her tact and niceness was reserved for work, or at least when work was the bar . It was not for nosy strangers with a thin veneer of false politeness and other bullshit clinging to their skin.
"Surprised you're asking so many questions, bikers can be nasty." A predatory grin to show that by bikers she meant her, it was a warning, like the rattling of a snake in the grass at the approach of a potential fellow predator.