Who is Eloisa from The Last of the Menu Girls and what is their importance?

Rocio meets Eloisa, a distant cousin, when she visits her mother's relatives in Texas during the summer. At first, Rocio idolizes Eloisa, who is more sophisticated, and is happy to traverse the town with her. Eloisa disappoints Rocio, however, as she is seen in the local movie theatre, smoking with her friends and allowing an older man to "paw" at her.