Friends a bad influence on dd

[Betti]

My 13 year old dd has made a bad choice with her friendship group. She is a grade A student who would never do anything to get into trouble at school. Since being with this group of girls, she has become more argumentative, has had detentions for being late to class, and has been involved in bullying other girls. I have intercepted messages from these girls who are encouraging her to self-harm (luckily there is no evidence that she is). She was always praised for being polite, kind and a nice girl but now her name is mentioned when people talk about the 'troublemakers'. I have told her that are friends aren't a good influence but how can I get her to drop them and go back to her nice friends?

She's going to be friends with whoever she chooses regardless of what you say or do and I don't think there's a lot you can do about that other than grounding her. However, the other behaviour, such as the bullying, needs addressing, and I would suggest starting with withdrawal of privileges like tablet, phone, laptop, games console etc. What have you tried already?

She has had access to social media blocked (but she just logs on with her friends' phones). I am encouraging her to find interests outside school in the hope that she will make friends with people who have similar interests. She knows what these girls do is wrong and assures me that she is not involved but I have told her that just being in their 'gang' is enough reason for her to be blamed. I know I can't choose her friends but I need a way to make her see that they are not good for her)

you said she's been involved in bullying. That is shitty behaviour that can actually damage someone for a lifetime.

tell her that. Tell her to stop being such a sheep. Tell her to think how it feels to be on the receiving end of her nastiness.

I hope she bursts into tears with shame - and then decides to be better.

The only way she'll give up those friends is when she finds something or someone she cares even more about. I know, I've been through the same thing with my now lovely lovely 15-yo daughter.
So don't just "encourage" her to find hobbies, you make her try things. The more demanding the better. In our case, we basically forced our then 13-yo to try out for a competitive sports team. She made the team, became very good at it in short order, and the intense practice schedule made it difficult for her to maintain her relationship with those girls. In the end, it wasn't that difficult for her to give up those girls because 1)she already knew those girls were not nice and that we disapproved of them, and 2)she made new, much nicer, friends on her sports team.
But it doesn't have to be sports, anything fairly intense will do -- theater, dance, or even a cause she cares about.