This may be long, apologies.
I am godmother to the 13 year-old daughter of an old and close friend. To say upfront I'm not religious but this is a formalised humanist relationship and one which was undertaken with seriousness and commitment. It's also worth mentioning that me and the friend are both single parents so we perhaps lean on one another more than if we were both married.
My god-daughter has been good friends with my 12-year old DD for years (they're not at school together). They were close friends for about 4-5 years and were inseparable. About 18 months ago there was an incident in which my god-daughter was breathtakingly unkind to my DD over WhatsApp. She and another girl ganged up on her, accused her of being a snitch and a baby and circulated a nasty video which was obliquely meant to imply my DD was a "chav". I flagged this to my friend/her mum and it was dealt with pretty robustly. The GD sent my DD a very sincere apology. All good at the time.
My DD was heartbroken and took it quite badly. I helped her with the fallout from this (which included speaking to the school counsellor), basically gently encouraged her to cut contact if she didn't feel she could trust the other girl. My DD voluntarily blocked the other girl, meet-ups stopped and they had very little contact for about 9 months to a year.
They re-connected fairly recently and have slowly been getting to know one another again. I've warned my daughter to be cautious and not move too fast with this and tried to encourage her to reframe the relationship, ie its great that you're back in touch but just take is slowly, remember it may not go back to being exactly the friendship it was. They've been back more sporadic contact for about 4-6 months, including a couple of playdates but in a more distanced way and I think my daughter is understandably more guarded about it.
More recently there's been a couple of incidents, not nearly as bad as the historical event, but in which my GD has been casually unkind and borderline spiteful to my DD (two recent examples: mocking my DD because she texted her an example of a piece of jewellery she liked and also complaining loudly because a playdate and a trip to McDonalds had to be interrupted because my DD had to go to A&E). It stops short of being something I want to raise to the mum and I increasingly think my DD needs to learn to be her own advocate here so I'm not getting involved unless it escalates but I am worried. My DD has stepped back again and has muted the other girl on WhatsApp etc but has not confronted her.
I guess my question is whether I should be gently steering my DD away from being her friend altogether., which in practice means me distancing myself from the mum.
I'm very aware that the other girl is right in the throes of puberty and probably in a difficult place. She's also a year older than my DD and may understandably want to spread her wings. It's difficult for me in my friendship with the mum if the kids cut contact altogether and I do feel some sort of moral responsibility for this kid who is my god-daughter. But I'm worried that my DD will put too much faith in a relationship with a child who doesn't seem to have her best interests at heart and who at the moment seems to display quite a nasty set of instincts and behaviours towards her.
I'm not inclined to force anything and will basically let nature take its course but I'm wondering how I should speak to my DD about it. She still refers to this child as her "best friend", for example. Should I explicitly disabuse her of this idea and steer her away from playdates (which in practice also means largely cutting contact with the mum). Or should I step away and let her work this out on her own?