Who is Rina from Dreamland and what is their importance?

Rina has been Caitlin's best friend from childhood. She is devoted to Caitlin, but she is also pushy, and it Rina's insistence that results in Caitlin being chosen for the cheer squad. Rina is described as a pretty, young woman, who gets a great deal of attention. When Caitlin enters rehab, Rina apologizes because she, as Caitlin's best friend, should have been aware of her problem.