This is what's going on... Aarti doesn't want to consciously hurt Yash, so she does everything in her power to save him from pain. But at the end of the day, Yash is choosing to give himself pain without her knowing because she has unintentionally hurt him so much.
So in short, the hairpin reflects what's really going on in their life right now. Aarti gets hurt by saving him from it, just as she does with the Prashant lie, but Yash eventually utilizes it to cause him a lot of pain, just like the Prashant lie is causing him an immense amount of pain.