Well, I am posting from lovely San Antonio. I talked to both my sister and mother in the last couple of days.
(Just as a note, my ex-friend is not a certified sex educator. She's a junior in college who volunteered this summer and worked in a federal program designed to teach inner city kids sex ed. But no certification was given to her.)
I think everything's okay. My sister wasn't angry with me, and we had a good talk about finding the right souce when you need to find something out.
My mom was a little upset, though, but she's not taking it out on my sister. She just made it clear that such things need to be discussed with parents.