After Chat leaves and Ladybug is left standing on the roof she shakes the rose she’s holding slowly. Like she’s thinking. It’s a difficult choice. To tell Chat that they can’t get to know each other better because of their superhero jobs. She doesn’t want to get his hopes up and even admitted that there’s a boy she likes.
She realizes that this is a dangerous job especially since a lot of people are at risk if their identities are discovered. She thinks with her head and not her heart for that will keep them safe but doing so may end up hurting her heart.
The girl is just as oblivious as Adrien is when it comes to love. Now that’s she aware that Chat loves her. She may have a hard time thinking her head now. Especially after that sweet kiss on the cheek.
I wanted to point out this scene as it’s something that’s can easily be missed. You can’t see her shake the rose very well in the gif (you can see it a little better in the video.) The rose really does go with her costume.