You cannot take any action against her. She has the exclusive right to marry and you cannot compel her. It does not matter that you both are well known and have had family relations. Tarnishing reputation is an actionable claim. If it comes under the purview of Section 499 of the Indian Penal Code, then you can initiate a criminal action.
In this situation she did not cause any act which is defamatory. Hence, you cannot take any legal recourse against her. It would be better for you to forget all those things. Don’t indulge yourself in any false legal cases. You are a handicapped person so you should look for a job. Don’t give up your aim of looking for a government job.
Currently you have no sufficient ground to initiate any legal action against her. She has neither committed any offence or any civil wrong. Refusing to marry is not a breach of contract. If she had shown her desire to marry you but later on her refusal does not enable you to claim breach of agreement. Consolidate your energy and put it in the right direction to be an independent person.