Actually on a subconscious level , she already started bonding with Manik in the storeroom and after he saved her from the cliff's accident but then Manik was back to be rude with her, and due to that she got a little bit confused... after after Rishab's wala scene, she saw through the real Manik. And that is where she started falling for him. His ensuring that his driver drop her home further reinforced her trust in him.
Then of course thanks to Navyaji she acknowledged that Manik was attracted to her and she even made peace with herself that he does affect her psychologically and physically.
Mud fight.. She realized and accepted that she was attracted to him as well.
Then the hug was another benchmark in the development of her emotional bonding to Manik. she could sense that Manik was in pain and she was touched that he came to find solace in her arms.
The next day when she soothed his forehead was another step whereby she internally wished to be the one to take care of Manik as she was now fully in tune with his feelings and the turmoil that he was going through.
afterwards when Manik said that the hug was a mistake, again another step whereby she realized how much importance Manik had in her life. It also gave her the opportunity to retro-inspect her feelings for Manik, and ofcourse the way she was ill at ease when Harshad mentioned that Alya would always love Manik.
Then the dance where she was fully aware of the sparks flying in the air, you can see at first she wasn't that into the dance but afterwards she got lost in Manik .
Then-after, the promise of Manik that he will never hurt her and that he trusts her.
Remember her definition of love: Trust!
And as she recalled the night where she was drunk, she remembered how Manik took care of her and she finally accepted her growing feelings for Manik.
She is definitely falling hard for Manik, But I guess she is a bit too shy to display her love for him right... It's all new for her, so she needs a bit of courage to voice out her feelings out and loud❤️