She should not have resigned until the job provided legal counsel.
She would have been fired if she didn’t resign.
FWIW, the department (almost) never pays for criminal defense lawyers. Instead, cops under a collective bargaining agreement usually have liability insurance paid for by their union. Non-union cops will sometimes have liability insurance as a employee benefit, either provided partially or fully covered.
Those that have no liability coverage either from a union or employer will have to buy it privately, which is not uncommon. It’s not super expensive, but it’s not nothing, something between $500 and $1,200 annually.