Gulp. My oldest is 9 so I haven't had to deal with that yet, but I've thought about it. Would I think I would do is not go into details but instead talk to her about how I decided I was ready for that step in the relationship. Perhaps you could even talk about how now you can see that it was a good/bad decision - share something that gives her insight and lets her know you are confiding important feelings to her about your own experience. I think by skipping the details but focusing on your feelings at the time you honor her request without oversharing.

I've had this talk three times now. I am always honest and answer truthfully. I explain my thoughts then vs now. What I wish I had known, what I have learned and how it impacted the larger picture. I think that your daughter is asking means she respect you and wants some guidance. My son, who will be 26 in November, was my first and I was so caught off-guard. I remember starting that conversation with, "I'm not going to tell you to wait, because I didn't...but what I want to share with you is the profound impact that single decision had on the rest of my life." My son gave me a hug and said, "I know my decision". I left it at that. 

Thanks. It's a frightening topic!

When they were younger, it wasn't easy to talk about, but now that they're "of age" I don't really have a problem with it. My daughter has a tendency to frown when I "don't act my age" however. I think she still wants Carol Brady, which I will never be!