Tamara Chen is apparently the only friend of Knives Chau. They're the same age (17). She likes The Clash at Demonhead.
She first appeared in Book 1 to accompany Knives to the Sex Bob-omb gig at the Rockit.
She appears in Book 2 to help Knives dye her hair and process the news that Scott has a new "fat-ass hipster chick" girlfriend, Ramona Flowers.
In Book 4 she comforts Knives after her (second) breakup with Young Neil.
In Book 5 she appears briefly to discuss Knives' plan to get revenge against Ramona, and then again at the end to discuss some new boy that Knives might like.