Is this police paranoia? Or, is it a normal response to a possible poisoning?

Slavish concern about job performance in an effort to maintain profitability of the establishment at all costs and a failure to understand the mission of the corporation as regards product quality.

Should she be arrested? No, that's a bit extreme. Fired? Maybe.

Police said samples of the burger were sent to the state crime lab for tests.

Well, if it's anything like Texas, it'll take months to get results.

Maybe somebody's dog within the chain of custody will eat the evidence.

According to the information above, she asked a supervisor and a co-worker, who both passed on the salty burger. If she's culpable, they are even moreso.