Coparceners mean a person who has equal shares with others in the inheritance of an undivided estate. 

Section 6 of the Hindu Succession Act, confers the status of coparcener (equal shareholders while inheriting properties) on the daughter born before or after the amendment, in the same manner as sons, with the same rights and liabilities. The Supreme Court held that this section shall be applied retroactively which means women can have the benefit of succession based on their birth making it unnecessary that the father of the coparcener should be living on September 9, 2005.

In a landmark judgement, on August 11, 2020, the Supreme Court has held that daughters will have coparcenary rights on their father’s property, even if the latter died before the Hindu Succession (Amendment) Act, 2005, became effective.

Danamma v. Amar Singh- In this case, the court stated that if the father is a coparcener who passed away before 9/9/2005 and a prior suit has been pending for partition by a male-coparcener, then the female coparceners are entitled to a share. 

 Following rights to daughters are provided under Section 6:

• The daughter of a coparcener cell by birth become a coparcener in her own right in the same manner as the son
• The daughter has the same rights in the coparcenary property as she would have had if she had been a son
• The daughter shall be subject to the same liability in the said coparcenary property as that of a son
• The daughter is allotted the same share as is allotted to a son;
• The share of the pre-deceased son or a pre-deceased daughter shall be allotted to their surviving child.
• The share of the pre-deceased child of a pre-deceased son or of a pre-deceased daughter shall be allotted to the child of such pre-deceased child of the pre-deceased son or a pre-deceased daughter.

MARRIED DAUGHTER -

After marriage, a daughter will continue to be a coparcener but no longer a member of parental HUF. She will be entitled to claim partition of property.

Even in the case of a married daughter who has died, her children shall be entitled to the shares that she would have received if she was alive on the date of the partition. In case none of her children is alive on the day of partition, the grandchildren will be entitled to the shares that the daughter would have received on the partition.

For more clarity you can check out https://blog.ipleaders.in/evolution-daughters-right-property-india-step-towards-equal-rights/#:~:text=The%20Hon'ble%20Supreme%20Court%20of%20India%20held%20that%20daughters,(Amendment)%20Act%2C%202005.

Hope my answer helps. 

Thank you for your valuable opinion , it appears that if the married daughter is not alive on the amended date then her share in the coparcenary property vanish and does not pass on to her Class I heirs. However if she is alive on that date and she dies afterwards then heirs can claim rights for partition or can retain their share in the ancestors property.