I saw some symbolism in the scene between Arshi in Arnav's bedroom. I'll try to put across my thoughts here. Hope it makes sense.
Remember the scene where Anjali puts on Shyam's ring in Khushi's finger? Well today's scene to me was a throw back to that scene. Anjali gifted that lehenga to Khushi (the lehenga here is symbolic of Khushi-Shyam engagement). Khushi wore it but only for a short while because the lehenga and by extension that relationship was not meant to be.
The lehenga choli tears and in the process exposes her body much like how her engagement with Shyam breaks and exposes the vulnerability of her family honour and Anjali's marriage. Khushi tries to mend the tear in the lehenga choli much like how she tries to address the problem which not only ripped her family but also threatened to rock Anjali's fragile marriage.
Before she can embark on her mending activity she needs something to cover herself with while she is at it. She has nothing but Arnav's shirt to take recourse to. Now the white shirt is symbolic of Arshi's pure relationship which was Khushi's cloak of honour as she went about mending the damaged family honour by getting Payal and Aakash together.
However, in the hurry she was in restoring peace and happiness to her family she fails to take care of her delicate relationship with Arnav and ends up tearing it by her thoughtless action.
Although Arnav is furious with her for belittling his pure love for her (much like the way she ruined his perfectly good shirt), he is forced to put up a facade for the benefit for his family.
Edited to add:
1.Khushi's payal (which belonged to her mom) slips out of her ankles and she gets her mom-in-law's kangan in her hand. This is symbolic of her leaving her maayka and living with the sasural.
2. If Shyam's vice-like hugging of Khushi at the terrace ruined Arshi's relationship - the tear in the shirt, Khushi's words damaged theire relationship even more - the lipstick mark she ended up inadvertently leaving.
3. Khushi has got her mom-in-law's kangan, even if it was given unwillingly by Arnav. So indirectly her blessing is there for their union (a point made by Sandhya from Dia's blog).
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