Legal Question in Civil Rights Law in United Kingdom

Have you tried discussing the matter with her, informally and politely? This is often the best way to deal with a matter like this, rather than involving a third party.

If she does not respond reasonably, then, there are other options. If you live in a flat/apartment block, you could discuss the matter with the person in charge of the building.

If nothing else works and she is just doing it to annoy your family, then it may be worth going to see a solicitor and asking him to write her an official letter of complaint. Often people will get scared easily if faced with the prospect of solicitors becoming involved in such a matter.