Hi. I'd like some advice if anyone has any.
DD(15) has had a friend since primary school who I've always had some concerns about (or at least I've always had some concerns about the friendship).
This could potentially be a very long post, but I'm going to try to keep it short.
Friend certainly has some nice points, and DD and Friend have been very close at times (to the extent that it was problematic if DD wanted to see someone else - Friend could get controlling in the past), but there are quite a few manipulative behaviours from her which I'm really concerned about in relation to DD.
She's always known EXACTLY how to push DD's buttons, and wind her up to the point that she will lose her temper to some degree, and then friend will smirk, or find a way to get DD into trouble about the temper loss (this was more true at primary school), or whatever.
Recently, friend has started to post pictures of DD (not really bad ones, but ones DD doesn't like - she's really self-conscious) online, and when DD asks her to take them down she will often refuse to do so. She'll just repeat "take it down please" in a mocking mimic, or say something like "of course I will", then later when DD asks again she says "I never said that. Stop being so serious and get over it". DD says this girl's behaviour makes her "feel like she's going mad". She's properly distraught, but says she doesn't have enough other friends to create any distance. Also, if I suggest DD distances herself she says "I can't do that because Friend will tell everyone all my secrets/turn people against me" or similar. Friend seems to be really popular (and considered very beautiful, is generally admired, good at organising fun activities, etc). I've always felt there was something a bit "off" about her emotionally (e.g., sometimes feels like she feigns empathy rather than actually feels it).
I've suggested I talk to Friend's mum, but DD has told me in no uncertain terms that I may not talk to ANYONE about it.
Is there anything I can do? I'm getting worried about some of the things DD says (particularly about how the "friend" makes her feel like she's "going crazy").