section 9

My sister had C-section 5 month before . She had a girl child . After that she face a major operation and her uterus removed. She was in the ICU for 22 days . Because my sis had a girl child my brother in law not even present and not even concern about my sis health .for this my sis send a legal notice to her in laws for their ridiculous attitude asking her about her status in her in laws . she is in my house for 5 months as she is not do good in health and with 5 month child and as per Hindu rituals. Now my brother in law filed a case as per section 9 on my sis on ground of his parents are ill and my sis not concerning their health and alleged that she is showing cruelty to her mother in laws when she was at his house 9 month before . And saying after several approach she is not coming in laws house which is not true . How to deal with this?