no I think she will wear a saree to make his mood lighten up like you said and go to the poolside as soon as she sees the rain...and here on the other hand, Arnav will remember the words Anjali said and her pain and he will realize that Khushi is alone and may say "shit Khushi is alone" and he rushes back to his room to find Khushi at the poolside and as it rains already, he will get smithen and memorised by Khushi's beauty in rain with her wet angelic face and will slowly come to her and try to get cozy with her, but as always the interruption will happen!
Yeh i thote rain sequence could be on poolside too first but when someone said he is going to leave her.. Lets see, theres definatley going to be an interruption so its most likely poolside. Or it could be arnav imagines it all but khushi has to wear saree some how