If you asked Marinette what she thought about Adrien, she'd tell you he was sweet, quiet and a bit shy and like a Prince Charming. If you asked her about Chat Noir, she'd say he was loud, exuberant and silly.
Slowly Marinette realized that chasing Adrien was like chasing a shadow, you can see it but can't touch it only stare at it until the dark of night came and it faded away, but Chat was like the sun, baiting everything in his warm glow with his smile and laughs.
Chat was there for her, ready to hold her hand through everything, not that Adrien didn't help her but with Chat everything was different, his view on things made her smile and laugh, with Chat she felt alive, she felt free.
Each times he'd poke at her, send her flirty grins and awful cat puns, her heart would flutter in her chest, her belly would fill up with butterflies and her eyes would sparkle. Adrien was only a precious friend these days and it was becoming hard to get Alya off her track when she'd say she didn't want to talk to Adrien but she and Alya were friends for a reason and Alya would soon know she was crushing on someone else.
So maybe she'd accept Chat confession the next time she saw him, he did say he'd pass soon to see her and who knows perhaps she'll finally tell him who Ladybug is but that'll come with hard work, she wanted to make him sweat a little.
If you asked Marinette who'd she'd immediately go to with a problem she'd say Chat after all she's always preferred the sun to the shadows.