What was the deal with that foreign store lady in the beginning?

Why was she pestering those customers so much and basically speaking and doing everything to PREVENT them from buying a cup of coffee or even buying practically ANYTHING in that store and providing a completely UNhelpful service, and then later driving at least one of those members crazy to the point of shooting her?

Isn't that her job to sell, isn't the point of a shop to help make profit? Was she just in a bad mood, inexperienced or trying too hard?

What do you think, thanks.

(Yeah, and I know that it is only ONE of the handful of downright bizarre, strange, controversial and even disturbing things happening in this weird late 90s cult black comedy crime thriller flick.)