For the overall storyline of Lila
She’s going to start as a minor character, just someone who doesn’t get much focus, you hear her say things sometimes that later rewatching (or if you know she’s the villain) don’t quite add up
A lot of the villain attacks she gets caught up in but several times gets beneficial things come out of it
As things build up, she gets more attention in the episodes, especially after it’s revealed that she’s the one creating akumas
She throws tantrums when she’s foiled and often her plans don’t work quite the way she wants, a lot of times with marinette benefitting by accident since she’s a good person and does nice things consistently without need for reward
After she loses the butterfly miraculous, no one has evidence it’s her so after staying quiet for a bit to see if the guy who stole it from her would rat her out, she starts building up a following in the school
She says something at one point about ladybug that marinette knows isn’t true but can’t prove it since she can’t say why she knows but it puts marinette on guard
Unfortunately, marinette is suffocating under her many responsibilities and can’t spend time trying to disprove things Lila says but many of the lies are about things that aren’t easy to prove or disprove
Eventually, when marinette learns to ask for help and prioritize, she starts being a louder voice against Lila which marks her as an enemy and Lila starts trying to undermine her and turn people against her
It’s a slow build up over several episodes, maybe even a season, but it adds a lot of stress to marinette, even if none of the class turns truly mean to her, they do start to doubt her some
At some point in time, she does start latching herself onto adrien without his consent and part of the lesson in that episode is in part that guys can be harassed to and they don’t deserve to be touched if they don’t like to be (good lesson for kids of both genders)
At the end of the show, Lila ends up having lost all trust and credibility in her class but with a chance of getting and doing better since she is just a kid at the end of the day