You will probably find that when kids go back to school, it will quieten down abit at that time at night, but the Summer holidays is only 6 weeks away roughly, and there off for at least 6 weeks, some 7! So maybe if your mum was to speak to the lady of the other house hold, It may be handle better lady to lady! No disrespect but women can talk for hours and about anything, so if they have some common ground, you may find that it will be resolved sooner and smoother than you think!
Other than that, others have posted advice with regards to the local authourities, and i would use that as the nxt step i the above does not work! You could also use your local county councillor for advice, they may be able to lean some weight on to higher authourity for you! Tell you mum to hang in there, thats her home, Dont let her give it up without trying all angles first!
Good Luck!