Can anyone tell me some information about Thimilar (in Arali, Vaddukoddai) caste in Sri Lanka?

Please don't mistake me. My friend, she need help. She is 'Koviar' Caste but she has been going out this guy for more than a year, this guy is 'Thimilar' Caste. Some Tamil parents are so crazy about Caste so Will they face problems from the family or is the both caste similar in the level? Please, she is really confused?