Can my brother recant his stament after lying under oath and can my sister still plead insanity when she didn’t?

My sister in law is 37. She is a paranoid schizophrenic. She does not take her medication and needs professional help. Her and my brother argued and she ended up stabbing him. My brother told the police she did not stab him but the evidence from the knife proves different with his blood and her finger prints. No one was there to see her stab him in the apartment. The only witness was a lady who seen my brother run in a store to get help and then seen my sister come in after. The woman testified from what she seen when they ran in the store that was it. Also my sister came to the hospital to see if our brother was ok. I'm sure that tells the police something. I believe if anyone in the right mind would not come to see the person they stabbed if they wanted to hurt them. I believe they would run but she didn’t. I was very worried. She has had episodes and hears voices sometimes not remembering what happened. My sister did not plead insanity and told the police that she didn't do it as well. Very sad this has happened. I personally believe this is due from her not taking her meds. Other than that her and my brother are best friends! Do they still have a fighting chance to save each other from being charged? If recanted his statement? And told them she’s mentally ill? Knowing he can't talk to her. I hate to see me lose both my older brother and sister. I am only 20. My brother is 30. They are both amazing despite a mental illness that has not been treated properly. I wish I was a professional at this point in time.