Now, if a magistrate signed off on throwing her in jail for not returning a videotape 9 years ago, then there's something very wrong - the magistrates are there to filter out exactly this sort of BS from wasting the court's time.
It's likely there was no magistrate involved today. The warrant she was arrested for was issued years ago, the police only now caught up to her and are acting on it. Warrants don't expire (apparently), so it's good enough to have her arrested and held. They don't need to ask a magistrate to hold someone with an active warrant.