It's rude to snap at someone.
Stacy's coworker is really bothering her with constant yammering and distractions.
Stacy wants her coworker to leave her alone to do her work.
Stacy takes some time to gently tell her coworker that she needs some quiet while she's working.
Once Stacy has lost all patience with her coworker she yells at them to shut up.
Stacy's coworker leaves her alone while at work from then on.
The coworker is deeply hurt at being yelled at just for being friendly and never talks to Stacy again.