Believe me, my mom was always wanting to know that stuff with me. I HATED talking ANYTHING adult with her. Its not that I was mad at her, or think her not wise or anything I JUST HATED IT. My mom had a habit of making more of a deal than it was, she would get all gushy, and try to tell me things i already knew. I didnt ever come to her for anything relating to puberty or sex. I learned most of it myself. SHOCKING I know. I was a little more advanced in learning so I did lots of reading. My friends in school told me most, and only some of it was wrong. She also didnt know I had my period until my sister complained I was using HER products. Then she really went all drama on me for not telling her, she bemoaned, she whined, she even loudly said to where the family could hear, about I dont trust her, I dont care to mention anything. I vowed from that moment forward she would NOT know anymore things about my personal life. I know she was just trying to help but she bugged me to no end. If she is more comfortable with the older sister, ask older sister to inquire and report to you occasionally. Sometimes shy girls are more likely to talk to a nurse at school or a aunt or cousin she is more comfortable with. If she one of those, occasionally ask them to check on her and see if she needs more advice or questions answered. I can tell ya if you outright ask her it will make her more secretive. I wasnt into anything bad, I didnt have sex till I was 19 I didnt do drugs or weird things. I was a normal, shy teen. I am a fine, well adjusted 36 year old with 3 of my own kids, 2 of which are girls. I wonder what they will be like when they hit 14!