OH My Gosh Where is SARAH ???

YUP that's what I was screaming last night when everyone one left the party, I turned around and Sarah was GONE! We split up and started searching calling for her, you name it! Couldn't find her anywhere! I Then remembered back to when she was 3 yrs old and she stowed away into Stacys car so I Called her and just as I started to dial her she was back into my drive way pulling Sarah out of her SUV. I was relieved scared and MAD as Hell all at the same time! Needless to say she is Grounded, not just no TV but grounded to her room. What's Sad is the other little girl put her up to it, this little girl is often mean to her and Sarah just wants her to be nice to her so when she is asked to do something by her she jumps on it I guess whether its a good thing to do or not. So Is this a sample into teenage years even more so? How do I break this cycle with her? My heart is breaking for my baby. I feel like I have failed her miserably.