Hi
1) If your rental agreement stipulates a monthly rental and also some terms and conditions as long as you abide by the terms of rental agreement, the owner/Police/Any Court cannot ask you to vacate the premises.
2) Also the owner is bound to take care of maintenance of flats( Air conditioner, Electrical and Seepage Problems) so as to let the tenant enjoy the possession of property. It is her pristine duty to keep the flat in good condition and order failing which she is not entitled to receive the full rental.
3) As rightly pointed out by you, your land lord(lady) is making lame excuses and forcing you to vacate .
4) Her lame excuses clearly outline her evil intentions of forcibly trying to vacate you (how is it possible for her brother to set up an office in a residential community) and also under the guise of selling of the flat.
5All you need to do is the following
5a) Keep paying the rental month on month in to her bank account.
5b) File an injunction petition in the court restraining her from forcibly evicting you. Once you file the injunction petition , she will then realise that she has to fight a legal battle which might drag on for years and instead might offer you a good will amount (5 times/6times) your monthly rental and ask you to vacate .
Hope this helps.