I absolutely love to talk about this😉
Okay..... So Aryan was not at all interested in her because of how *jungli* she is🤪
But then when he got to know her and what she was capable of, he was filled with utmost respect for her. Her pain, her vulnerability, her resilience amazed him and he started to feel weirdly protective of her. There was no specific occasion when he fell for her... It was a gradual process. But i still think it was during Aditya-Malini wedding track, particularly during the whole DDLJ makeover, he started to develop romantic feelings for her. During their own wedding is when he realized he was madly in love with her and became aware of what he was doing to her... So he let her go. And the rest is history.
Imlie was always in awe of him at first. Though they dint show her side of the story properly, but what she feels for Aryan is what I actually call love. He was her mentor and her friend. Dunno if it's only me overthinking but i think the first time she got an idea about him when she made fun of him about his love-life during the Malini-exposing track(it's my favorite scene).... that his feelings are not to be messed with and the man is not merely a calculative businessman. Damn it's so confusing when it comes to her (damn you writers) but i think she started seeing him beyond mentor during Arpita's and his accident. The forced marriage was a speedbreaker And i also think she started seeing him as her husband when he openly declared his trust on her as his wife. She was saddened when she saw his vengeance but eventually became aware of what he was going through after he got his head bonked again. She realised her feelings after a near-death experience in the Purandas track. Baaki ka toh sabko pata hai🤪