False alllegation of theft, robbery dacoity and house trespa

No need to worry.

First, it has to be seen that the complaint lodged by the mother-in-law has been reduced into FIR or not.  Secondly, your statement shows your innocence.  The I.O. will place his report before the magistrate, saying there is no cognizable offence appeared to have happened in this context.  If the I.O. feels there is some offence happened, he would place his report before the magistrate.  It appears to me that I.O. (investigating Officer) would adopt the former course.

Now, "Protection of women from Domestic Violence Act, 2005" is in operation.  Under this Act, a wife can file a complaint against the male members  (note down, not against mother-in-law)of the husband's family and there are stringent provisions are there in this Act.

After going the entire facts related to the matrimonial life of your sister, with the aid of competent local advocate, a case can be carved out aginst the male members of the husband's family so that it will deter the mother-in-law not to harass you and your sister with false, baseless and inhuman criminal cases and also withdraw the complaint against you.

In addition to this, if the facts support, your sister can file a case under Section 498-A of the I.P.C. against the husband other family members including the female members.  But make sure, that innocent persons of the husband's family shall be left free and not dragged in criminal case in the interest of justice and morality. 

It is such advice of Advocates (what learned advocate Prabhakar has suggested) makes all the women welfare legislation a farce.

Well, in india, anybody can make any allegation against anybody for anything. The acquital rate is almost 99%. False accuser is never punished. This criminal justice system is a mockery of justice.

Thanks to all of you, I would like to elobarate on this issue.
We got my sis marriage done the way they asked and statisfied all their needs. Even after that her MIL did demand money from her, she did ask her 4 years saving money and her monthly salary. When my sis didn't give then she tortured her mentally and treated her like servant in their house. And later husband also did demand money and said without giving money he can't take care of her, so she decided to leave the house and packed her things and when was about to leave her MIL did manhandle her and asked her to give written statement the way she wants, my sis refused and they tried to lock her inside the house. My sis shouted for the help and some one out side person came so they left her. After one week she came to know she is pregnant, so her husband came and promised for good life and will not demand for money and took her back. After 1 week he did demand money and her jewels and left her in our place. So next day I went with her to take her cloths and her vehicle. At that time they locked us inside the house and called police. 2 police constables came and her MIL did start telling false story and we asked police to check the things which we were taking they said it;s family matter and they will not do it. Her MIL told to go to police station we were waiting with constable and then she said she will not give complaint. So constable told us to go, I got an auto and sent my sis and was about to take her vehicle and her MIL told tht will go to police station. So I went to police station with 2 constables, she gave complaint. Without knowing the content of the complaint, I gave statement as dowry harassment with my sis and so we just took her belongings.

Police did not investigate further as this was family matter. Then after 1 month my sis husband made a rented house and took her, and there within one month he did beat her badly for not giving written statement and apologize letter for his mother and locked her inside the house. I went there to take her back and he did fight with me and was unable to take her cloths. I called my brother-in-laws and that time he kept quite and we took her clothes and got her back home. And then went to hospital and got MLC done and after 2 days we gave police complaint against her husband and MIL for beating. And it was not a FIR. we could have lodge 498-A, but we thought he will become alright after her delivery.
During this time my sis MIL with the help of other elders and neighbours tried to pursuade my sis to come to their house. But my refused go to MILs place. my sis  told she will live with the husband if he makes a separate house near her parents place. Nobody agreed, so talks failed. Then her MIL went to court got the directive to investigate regarding this case from DCP. Now, ACP is investigating the matter. She has also alleged my sis to be having adultry and she has also applied for restitution of conjugal rights. My sis father in law is no more. Her MIL knows a little bit about law, thts why she is troubling her like this. Now can somebody tell us what we can do? we have consulted a local advocate...he is telling relashionship will be broken once for all if u file 498A.. he is telling to file defamation case against them and ask for compensation. I am really very much confused as what to do next? kindly somebody please clarify?

Is it wise to take anticipatory bail at this point of time and what will be the expenses for taking anticipatory bail. Please suggest me something...

Generally anticipatory bail is taken once FIR is lodged.  Otherwise also, if a complaint is lodged against you and the police is investigating the same, there will be naturally apprehension in your mind that you would be arrested.  In these circumstances, anticipatory bail will be taken.  The application lies before the Addl. Sessions Judge and the Magistrate has no power to decide anticipatory bail application.  If anticipatory bail application will be rejected, then one can approach to the High Court, but clearly indicating the fate of the anticipatory bail application before the Additional Sessions Judge.

After saying these generalities, I advise you to contact a local lawyer (preferably woman lawyer, who can understand the problems of domestic violence) and move anticipatory bail application.  The fee depends upon the lawyer to lawyer and place to place.  As you are a doctor, it is within your means.

Wish you best of luck.