Lucy gets along with Luna tolerably better now, and sometimes pops up like a ghost to check up on her sister. So that would work nicely. She might have been intimidating towards him initially because strange boy around her sister but cooled off when she got to know him better.

And probably passed him some shoplifted item to hide in his backpack because they wouldn't search this upstanding responsible student. Or encouraged casual trespassing. She's an A+ influence.