My ex S_i_L respected her 14 year old daughters privacy, and trusted her to rely on mum's guidance about the internet. that's why at her daughter became a mother, the nice "school boy in her year" she met online was 7 year older than he claimed.
Like I said, it goes hand in hand with good parenting and guidance. You don't have to spy on kids to achieve that. Why was this kid in a position that she was meeting people she'd only met online? Did her parents not know where she was going or who she was with? Even if she did manage to sneak off and have a relationship, wasn't she taught about condoms?