Doesn't it affect the sale of a property if the seller has to declare that they have had a dispute with a neighbour? I thought that type of thing had to be declared when a property is sold? If so, perhaps suggest this to your landlord and ask him/her to soundproof your flat if possible to avoid this Maybe do that, and then as has been said already perhaps put rotting fish etc through her letterbox the next time she goes away for 2 months