Hi Sazzle,
I am assuming you have a leasehold flat, in which case your lease will have the same terms and conditions as the flat below and all the other flats in the development. It will contain a series of covenants (conditions) some with the freeholder and some with other owners/occupiers - so depending on what she is breaching, either you or the management company could take action. Landlords can also be held responsible, in some instances, for nuisance emanating from their property under civil law. Both of these are only actionable in the civil courts and could cost you a fair amount of money to pursue, but some strongly worded letters from a solicitor may head things off.