Is it allowed to give monetory help for a girl who may marry a Hindu. He asked me money to get her daughter married. I have promised him long back that I will help him in his daughter's marriage

In our place most of the muslims follow Hindu customes.They go to temples also. May Allah bring them in to correct path.My uncle is also like them. He asked me some money( he will not return it to me)to get her daughter married.Ofcourse I have promised him long back that I will help him in his daughter's marriage.In our place bridegrooms demand dowry(some money) from bride's parents.To give dowry my uncle asked me money.Actually I think he is going to give his daughter to a non-believer.I don't know about my uncle's daughter , whether she is a believer or not.My question is (1)Is it permissible myself giving money as it may be resulting in my uncle giving her daughter to a non-believer. Or do I have to do her marriage with a believer only(If I take the responsibility of my cousin sister my uncle may give the responsibility to me). I stay out of my home. Now I am staying in UK on my job.I may go to India after 6 months Insha Allah.If I go to India also I stay very far from my native place.It is diffificult for me to search a believer for my cousin(uncle's daughter).Our uncle is in hurry to do his daughter's marriage.What should I do? (2)If I give money to him for his daughter's marriage.Is there any fault on my part if he does his daughter's marriage with a non-believer?I think he has seen one match. I think he is a non-believer. He wants to give his daughter to him.