Hello I am a solicitor with 20 years experience. I will try to help you with this.
Is her landlord a private individual or a social landlord?
I don't know I think a letting agency bought it but i'm not sure
If you know who the landlord is you could approach them and they might take action as there is bound to be a clause in the tenancy agreement banning illegal conduct in the property. However you could not compel them to take action.
You could call the police but all that is likely to happen then is that after a few hours in custody and with the prospect of a fine she will be back and not very happy about things.
so your saying if the landlord won't do any thing there is nothing I can do
In practical terms I fear there is no effective legal remedy for you.
Yes that is what I am saying.
good and quick reply