according to me, both were impulsive and foolish decisions. Like you pointed out he asking her to marry and she agreeing to the marriage are the most foolish and the other two are aftermaths. I mean, Ka didn't even bother to change in to a white sari, did she know that shes going to be getting married within the next 24 hours and therefore decided to stay in a red sari? ❓
And i also know the robbie may be considereing raunak the worst friends ever. And that he think ra betrayed him etc. etc. but the dude just died! At least wait, for i dont know lets see, 2-3 months before getting married to his wife!
I know its a serial and it has to move on but they could have had a three month leap or something.