A young woman’s life turn upside down when she joins a secret agency to fend off her bullies.

I'm still not seeing a clear connection between all your elements. What is the inciting incident for your story? Why would a secret agency arrest a random girl for weed? Why would they let a random girl join said secret organisation? And what does that have to do with her being bullied? I'm struggling to think of a way to put all of these elements into a cohesive logline which IMHO means something is missing

1) She was arrested for possessing weed.
2) She lost her sister from cancer.

The event could be that she begins being bullied and that's what pushes her to a secret agency. But I'm not so sure how you'll be able to connect those two things. If it's a secret agency how does she know about it. And why would bullies cause her to somehow find the agency?