Juanita Fulano, I'm sorry

I don't want to give her real name, but she is one of my greatest regrets. I had been in the mission (located in South America) for two and a half months and my companion and I were teaching the mother of an inactive member. She was very nice, and always had a hot meal ready for us, despite our insistence that we had already eaten. We progressed through the discussions quickly, and mother and daughter returned to church for two weeks in a row. On the day before her baptismal interview with the District Leader (and just two days before her scheduled baptism) she told us about an interesting movie she had seen on television.
I'm still not sure what movie it was, but apparently it featured Brigham Young and at least some of his wives. Obviously, this was the first she had heard of polygamy and she had some questions. My senior companion was handling the "resolve concerns" phase of the commitment pattern. I was shocked to hear him tell her that there was no polygamy in the Church and that Joseph Smith only had one wife. At this time, I was mostly unaware of Joseph's sticky marital situation, but I thought that he had at least one other wife, otherwise why did Emma get so mad? Of course I wasn't certain about all this since it's not exactly in the curriculum at the MTC or in Seminary. So while I thought he was telling the sort-of truth (and I'm sure he probably thought he was too), he was certainly not being honest with her.
I opened my mouth and promptly shut it again. Could I have said something? Sure, I could have tried to explain the history of polygamy, and explain why we don't follow it any more, but I doubt I could have done it satisfactorily then or now. The heart-breaking thing is that she probably would have accepted the Church's past polygamy had we told her about it. She was golden. But instead we chose the coward's way out, and kept her in the dark so she would definitely get baptized. My companion went on to become ZL and I went on to become an eternal junior companion.
I try not to think about this and similar incidents from my mission often because they really disturb me. Like many other shameful episodes in my life, I try to put this out of my mind and pretend it never happened.
Is Juanita Fulano inactive today? Probably. Is she inactive because she found out about polygamy? Probably not. But she still deserved missionaries who lived up to the name on their tags.