If your wife has a disease, it is no crime, hence there is no question of seeking legal protection. But following are some of the precautions you should take-
1. Keep all records of diagnosis and treatment carefully. They might be needed.
2. If you seek a new insurance policy for her, do not hide this fact.
3. Get her treated well. You can be held legally liable if you neglect wife's treatment, especially when the disease is of a psychiatric nature. [NOTE--Treating her well does not mean getting treatment from costly private hospitals, which you may not be able to afford].
4. Take care that you don't leave her unguarded in situations where she can cause harm to self [Suicide]; or family [home, kids, car accident, credit card over-spending] or others [car accident or other violent act]. If she does any of those acts, she would escape liability but blame may come to you for not taking necessary precautions.
5. If not already communicated to her parents and brothers, do so now so that no blame comes to you later on. You must have proof that you have informed them about it.
6. If things are really bad, it would be wise to write a letter to the SHO of your police station on the following lines: This is to inform that my wife is suffering from mental disease as certified by doctors and is likely to commit acts harmful to herself or others. It is not possible for me to guard her all the time because I have to go on work. It is requested that a beat constable, preferably a lady constable, may be assigned to pay periodic visits to my residence . If the police station staff refuses to accept this letter under acknowledgement, send it to them by registered post, AD with a copy to Commissioner of Police. [I know that most likely, police would not accede to your request. But, this letter may help you at a later date].
7. If your wife enters into any agreement, such as transfer of property, the witnesses should specifically state therein that she is in a normal state of mind and is able to understand what she is doing].