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I don't think Chloé ever had actual feelings from Adrien.
Just think about it: they grew up together and held each other company when their parents were too busy doing politics, fashion, trying to heal their dying wife, average rich people activities.
And it could be the 'falling for my childhood bsf' trope. But seeing how Adrien treats, I'm convinced that they had a more sibling-like relationship (I dare you to tell me that Adrien doesn't talk about her like her annoying little sister).
Now if they really had this kind of bond, why did Chloé feel the need to pretend to catch feelings for him? Well, the same reason for everything bad she did (in s1-s3) : her dear old mother.
Bare with me now: the more Chloé grew, the more she felt the need to be like her mother. A fashion icon with an unbearable attitude and of course; a man by her side that is worthy of her. And who better to choose than the famous young model, THE Adrien Agreste, that also happened to be her childhood friend?
Chloé didn't actually love Adrien, she knew that. But she just convinced herself that it would come. Eventually. Cause who else could she possibly be with that would reach her mother's expectations?