Deb is definitely the lovable weirdo of Mclean's new friend group. When Mclean arrives in Lakeview, it's clear that no group has taken Deb in, and her new friends are shocked and appalled when she invites Deb to sit with them:
"Do you want to sit with us?" I asked her. I felt both Riley and Heather look at me, but I kept my eyes on Deb, who looked so surprised—shocked, even—that you would have thought I'd asked her to lend me a kidney. (5.196)
But they all realize that they've been missing out on a lot. Deb doesn't care what people think about her, and instead she just does whatever she wants. She gets involved in all these different activities because she likes them, not because she's trying to fit into some kind of mold—plus she's also an extremely loyal friend. So while some of Mclean's friends cringe when she first invites Deb into their fold, they quickly realize that they've been majorly missing out by not getting to know this girl who marches to the beat of her own drum.