In Brick (2005), Brendan asks Brain for the whereabouts of Emily:
Brain: Well, I know she's been poking in with the Ivy-bound cheerleading elite, Laura Dannon's crowd.
Brendan: Laura Dannon there on the Linc'?
Brain: And Brad Bramish. Cream on the upper-crust. Anyway, Em tagged after them for a bit, but it didn't work out. She picked her way down the food chain.
Here Brendan says Emily teaming with Laura Dannon didn't work out, so what she picked in way down the food chain?
I know "way down the food chain" is simply an English Idiom, but still what exactly does she pick here in form of food chain?