I dont think Unhappy is saying that for everyone. Your point is right ... I dont see any flaw in it.
Problem is that Ragini already decided and went for the marriage. Although its not the best thing to do, but she did it. And now, things which are to follow is obvious. Appu bhai is interested to bring colors and happiness (this was not exactly a required option for happiness, but then it was her decision as per Vasu).
See ... the description you gave is very nice. But that has not been followed in case of Ragini. No matter what circumstances, everything could've been tackled ... even if Ranvir would request, she could very well discard that request as an unfair and insulting demand. She should've shown her dignified identity (i.e. if she measured dignified identity as being loyal to her first love forever - and never let it get insulted/undermined/exchanged/compromised at any cost).
But then, if remarriage is her decision (no matter why) ... then the next best step is to fulfill the duties of being married to a good man like Anmol ... recognise that now ONLY HIM AND NO ONE ELSE is the beloved daddy of Tamanna (as she herself have hidden this from Tamanna ... the mother is the person who should inform Tamanna of her father). She should give the relationship (which already have been establised) a smile.
I think Ragini will give that smile very soon ... its just a matter of time now.