One-third of his property shall belong to his widow-grand mother and the remaining two-thirds shall go to his children. When property is already sold she cannot claim share in property. 

You cannot seek money spent on Aunty wedding 

she would be entitled to share in property 

See if grand father made will for his property then your father is absolute owner of the property. 

If grand father died intestate the aunt has right and all other legal heirs has to make relinquishment deed in favor of dad.

indian Christian law governed by Indian Succession act. if the father dies intestate then the daughter is entitled to get equal share in their property. 

your father cannot claim any expenses of sister wedding. 

There is nothing as ancestral property under Indian succession Act and property becomes self acquired inspite of the mode of acquisition.Men and women have equal rights in christian law of succession.

Since she's one of the legal heirs to her deceased father,  and as she was not a party to the transfer of this property to your father,  she is entitled to a share in the property,  hence she can claim her share at any time. 

Your father cannot demand the money spent on her marriage. 

This law is common for all Indian Christians. 

Dear

The law of succession for tamil Christians are governed by customary laws of your area.

But generally the inheritance of ancestral property of christian is governed by Indian Succession act and it says the daughters are entitled to equal share In property.