Your cousin sister is the daughter of the deceased female legal heir of your grandfather hence she will be entitle to a legitimate share out of the compensation amount towards her mother's share which cane be distributed by her to her own siblings (if there are any).

Her share in the compensation amount has to be allocated failing which she may file a suit against all of you for recovery. 

On demise of grand father ,grand mother his 2 sons and 2 daughters were legal heirs 

each had one fourth share in property 

on demise of sin his wife and children inherited his share 

on demise of daughter her share devolved on her spouse and children 

1. The surviving son of grandfather (your mom’s brother/your mama). One fourth share.
2. Wife of your deceased mama. One fourth share.
3. You through you mom. One fourth share.
4. Daughter of Tāyiya sahōdari. One fourth share.

Are the  legal heirs. Each will get ¼ share. You and mom will get ¼.

 Assuming that the property was self acquired property of your grandfather and your grandfather died intestate (without executing a WILL) and your grandfather's mother and your grandmother had predeceased your grandfather, then the property would devolve equally to all the children of your grandfather. In other words two sons and two daughters of your grandfather are each entitled to twenty-five percent undivided share in the property. Since one son of your grandfather is deceased, his share of twenty-five percent gets subdivided equally to his widowed wife and children. Similarly one daughter of your grandfather is deceased, her share of twenty-five percent gets subdivided equally to her children, including your married cousin sister, who is living separately from her husband.

Only legal heirs will get money she can’t claim money from husband as a matter of rights and he is alive she can only claim as matter of right after his death

The legal heirs of your grandfather in this case depend on whether he passed away with or without a will and the personal law applicable (Hindu, Muslim, Christian, etc.). Assuming your family is governed by Hindu Succession Law, here's the breakdown:

Legal Heirs of Your Grandfather (Died Intestate):

If your grandfather passed away without a will, under the Hindu Succession Act, 1956, his property would devolve equally among his Class I heirs:

1. 
   Class I Heirs:

   • Sons
   • Daughters
   • Widow (if alive)

Since:

• Your grandfather's two sons and two daughters were his Class I heirs, the property would be divided equally among these four.
• If a son or daughter predeceased your grandfather, their share would pass to their respective legal heirs.

Specific to Your Case:

1. 
   Your Mother: As a surviving daughter, she is a legal heir to your grandfather's property.
2. 
   Your Mother's Brother (Surviving Son): He is a legal heir.
3. 
   Wife of the Deceased Son: She can claim her late husband's share.
4. 
   Legal Heirs of the Deceased Daughter (Your Cousin):

   • The share of your deceased aunt (your mother's sister) would pass to her children (your cousin sister) equally.
   • Your cousin sister, as the sole child, is entitled to her mother's share.

Thus, all four branches (two sons and two daughters or their legal heirs) have equal entitlement.

Does the Definition of Legal Heirs Change?

The definition of legal heirs may change depending on:

1. 
   Personal Laws: Different religions have different inheritance laws.
2. 
   Type of Property: Ancestral property and self-acquired property have distinct rules.
3. 
   Case-Specific Factors: The presence of a will, adoption, or other unique circumstances.

How to Handle the Situation:

1. 
   Legal Distribution:

   • Ensure that the compensation amount is divided equally among the four branches (as per the family agreement).

2. 
   Documented Agreement:

   • To avoid disputes, all beneficiaries should sign a written agreement acknowledging the agreed-upon distribution.

3. 
   Counsel Your Cousin:

   • If your cousin's behavior is causing tension, you could explain her legal entitlement and encourage her to cooperate with the family decision.

Legal advice may also help mediate if the conflict escalates.

- As per law, after the demise of your grandfather intestate , his property would be devolved upon all his legal heirs equally i.e. his sons and daughters each will get 1/4th share in the property. 

- Further , after the demise of other son and daughter , their share would be devolved upon their respective legal heirs equally.  

- Hence, the compensation will also be claimed according to their respective shares, and hence the cousin sister after demise of her mother has right to claim