Depending on the state the (ex)employee is in, it can be illegal to withhold wages of any reason not prior authorized by the employee. As this was an involuntary termination(firing) the employee likely did not known it was coming. Depending on how she was normally paid it may have required payment at time of termination(depending on state again) so the employer may not have been able to deduct anything from a final check already processed/created.

With that said, everything ever in any company, security and HR basics book ever says you let the person walk with something and if you want to pursue theft charges you do so as a company. Most companies know people who are being fired experience a lot of emotions and it can put them in a state where they may act unpredictably. It may escalate into violence, retaliation by the (ex-employee), cause a scene, etc., none of which are anything approaching “worth it” for a company unless you’re talking about trade secrets or the like and not a $1.14 vest. Many employees/humans, when given the chance to take a breath and leave the situation would have returned the vest, but being treated like a caged animal yields predictable results for corporations who sees their employees as such.

Horrifying and unsurprising from Walmart where customers are/were funneled into violence chutes(black Friday) to save $50 on TVs each year with no thought to the bigger picture or safety basics.