For audience, Aditya and anyone else, Imlie demanding haq is just selfish and breaking her promise.
But but but if we think from Imlie's perspective it is totally justified because ...
She is demanding haq due to her history. She is not in love with Aditya, probably doesn't even like him a lot, but she has seen what her mother had to suffer throughout her life.
She has come from an orthodox village (though she tries to stay away from their orthodox mindset) and whatever she has seen in the village, she believes it to be the ultimate reality. A city man left her mother for good by making her pregnant, so the village has sort of outcast her just because she doesn't have her husband's name. Her mother has lived in misery throughout her life and this is the life Imlie is very scared of. That's why she never wanted to get married in the first place.
Now that according to villagers she is married, she fears that she will have to live the same miserable life her mother lived. Remember she still doesn't know how progressive things are in city, so she believes whatever she saw in pagdandiya as the universal truth. So her demanding haq is justified from her pov just because she doesn't want to live like an outcast for the rest of her life.