I can't really blame her though. Sure for us the idea that the Hero and Cop are scum who would frame someone for serial rape is kinda expected but that is kind of wild to think about in universe.Their plan to set him up wasn't even that good, the fact she believed them was pretty bad, I like to think if I was being set up like that and I insisted I was innocent my immediate would at least believe me.
And the Saint didn't even lie, as far as she knew she's been sending letters and money to her fiancee for ages. The idea that the church would embezzle all of it usually wouldn't cross someone's mind.
Though I'm not sure why the lady doesn't seem to understand how harsh her country's justice system is.