The police aren't being asked to enforce a civil action. Theft is a crime and the police do not need the victim to approve action against the criminal. They simply didn't want to follow up.
> It's the bank who was harmed
The women would have been out $500 if she had not noticed it and because she did, she had to report it to get the money back. Both of those are problems that she had/would of had to suffer through.
Local cops serve the local community. They're responsible primarily for deterring/investigating crime that most directly affects the local community. So if they have to choose between chasing some bank's $500 and the perp who broke into a someone's garage, they're going to serve the locally registered voter every time. And that's how we want it.
Banks are very good at managing fraud, on the whole. They tend to view it at the level of detection and prevention, not punishment (which is far more expensive). And their techniques work. Total fraud in the credit card industry is actually very low.