1. In your query, it's not clear as to whether Krishna's father died testate or intestate?.
2. Assuming that Krishna's father died intestate (without executing a WILL), then his share in the property would devolve equally to his spouse and children.
3. Assuming that Krishna's father died testate (after executing a WILL), then his share in the property would devolve to the beneficiaries in the manner stipulated in the WILL.
4. Since Krishna has a sibling (elder sister), she will definitely have equal right in the property share of her deceased father's share, if her father had died intestate.
5. Since Krishna's sister hasn't executed any document (as narrated by you), it's better to get evaluation of documents done by a Lawyer to know whether to proceed ahead or not?