13-year-old grand-daughter's behaviour.

I've posted on Gransnet before about my concerns about DGD's behaviour, but do feel the need to speak again now, about 18 months later.
DGD's relationship with her mother (my DD) has deteriorated even further than before. She screams at her and tells her that she hates her (typical teenage behaviour perhaps), but this happens all the time. There is no warmth or love shown whatsoever, though DD tries so hard to draw her to her emotionally. DGD has always preferred her father and tells her mother constantly that she wants her to go away and leave her to live with her dad.
Tonight the neighbours called the police because of the screaming and shouting that was taking place. The police came in, and spoke to DGD and DD , explaining that it couldn't be tolerated that neighbours were being disturbed in such a way. DD told me tonight that the neighbours had come to the door last year and complained about DGD's shouting at her mother late at night.
DGD is having no problems at school - in fact she's doing very well in all her subjects.
The only advice I could offer DD is that she makes a GP appointment for herself tomorrow and tells him how this is affecting her, and then asking if there's a route she can follow to involve professional help for her relationship with DGD.
DD has always been a 'coper', never asking for help with anything, but tonight she said, "Mum, I just don't know what to do."