Friends of 14yo DD. They've been 'going out' for some months. Very innocent, afaik. Girl is 13 (and a half), very innocent. Boy is just 15. He's a lovely lad.
DD told me that their texting had ramped up a bit and he asked a couple of inappropriate questions (which she didn't answer), one of which being had she ever 'sent a picture to anyone of her in her underwear?'. The girl felt very uncomfortable. They then were doing a text message 'truth or dare' and the girl felt that the boy was trying to coaxe her into a 'dare' situation whereby she disclosed quite intimate details about herself.
Girl is very uncomfortable, but insistent that she doesn't want to tell parents (which is what DD advised). DD pointed out that she should be able to firmly draw boundaries about what she's comfortable with. Girl said she didn't want to be 'not polite'. 
I've given advice to DD, and feel that if I interfered by telling either mum (both of whom I know well), I might do more harm than good, regarding trust of my DD to confide in me, and girl's trust in DD to keep a confidence. I'd rather she told me this stuff so I knew what was going on.
AIBU?