To the topic at hand, I am not versed in the theology being discussed, but as a little girl, in a Catholic school, I remember the great irony I felt when the snarky boys in my class got to be altar boys; while the Sisters (who by my assessment at that early age) had devoted their lives to their faith and their Church couldn't enter the Sacristy area. Gladly (IMO) the Catholic church changed that way of thinking. Anyway, I hope this woman (the teacher in question) finds a church that she can fully participate in.
I like what the nuns do. They teach kids, the administer to the sick and poor, and they run hospitals. But I'm also a fan of Catholic tradition that allows only male priests. I don't think it will ever change and I do not want it to. But as far as teaching sunday school, I think its perfectly fine.