I was a 17 yo virgin and so was she. 

 At our local Baptist church, during the evening service, I masturbated her to orgasm.  I had no idea what I was doing but she enjoyed the results. I secretly slid my hand under her skirt, over her thigh and into her knickers  A few quick kisses and necking  My fingers found the right spot and she quietly orgasmed  

 The only problem was that the preacher was also aware of what we were doing.  On the way out after the service he instructed her to attend counseling sessions with him. 

That was our one and only sexual encounter and  we are still friends.