Sounds to me like the simplest solution and biggest failure (aside from the whole concept of criminalization of possession in the first place) is in our public defender system, which seems to be a much wider-reaching problem. The fact seems to be that people who can't afford a proper attorney just aren't getting even marginally acceptable representation in many cases. We need public defenders with the time, resources, and incentives to actually provide a reasonable defense and legal advice to people who can't afford a lawyer.

In this case, it seems like a decent lawyer would be able to hear out the woman's story, and say something like "Hey, the lab will confirm the substance, so if you're really innocent, you should hold on, because a felony charge will ruin your life a lot longer than sitting in jail awaiting trial would." Instead, I'm guessing the lawyer had ten minutes to spend on this case before he had to move on to the next one, so he can't really do more than push the plea deal and move along, and there's no significant incentive for him to do more anyway. In fact, he'd probably get canned if he stopped to take appropriate time with each client, because then he wouldn't have time to even get to all of them.