Ragini agreed to marry Shishir cause she felt it her "Farz" or duty towards her family, her parents, and since she accepted this it ofcourse meant separation from Ranvir.
Now i agree the separation part does and will make her sad, but if she has given more importance to her "Farz" and is giving up her love, then should she not do it with atleast a smile on her face.
In thursdays episode, the whole time Ragini was sulking, depressed, sad. If you are doing something for ur family especially parents, even though u do not like doing it u still do it with a smile.