In short, wanting to get her brother off drugs is a motivation, and as it turns out, it’s sort of secondary to saving her brother’s life. She wants him off drugs in general, but her goal—specific to the boundaries of the movie—is more like “save his life” because staying on drugs keeps him tied to a group of friends, who get themselves into a really bad situation as the movie develops. Keeping him off drugs is a Requirement. That puts it squarely in the OS.
Also, although it’s her motivation, it’s not her problem. That really has to be something much more specific and unique to her, and it was almost so obvious that I couldn’t see it: she has to weigh How responsible to I have to be for my brother?
That puts her into Mind and makes it unique to her.