When Ridley Scott saw Susan Sarandon's audition for Thelma and Louise, he said that she was Louise. In other words, Louise's qualities of being tough yet nurturing, in control yet vulnerable, and fierce yet kind were qualities shared with the New York—and, at the time, staunchly anti-Hollywood—actor herself.
So let's talk a little more about Louise.
We first encounter Louise at her job as a waitress in a small-town diner. She's telling a couple of young girls who've pulled out some cigarettes that "smoking will ruin their sex drive"—then she promptly lights up in the back. Louise wants to protect, often at the cost of her own safety. We know by the end of the film that Louise has been through some of her own crapstorms, to put it lightly, and yet she'll stop at nothing to protect the ones she holds dear.
As we find out, she'll even kill for them.
Louise has a flaky boyfriend, the run-around musician Jimmy, with whom she wants to settle down. It's clear that Louise's life is ordered and prim, except for her touch-and-go relationship. (Who packs their shoes in Ziploc bags, for real?) But it's also clear from Louise's attitude that she won't wait around for anybody. Friends come first with this one.
Despite her often steely exterior, moments of Louise's vulnerability are dabbled throughout the film. Take this phone call, for instance:
(Louise sits on the edge of the bed. She is looking at her hand.)
(She takes the ring that she wears on her left hand and turns it around backwards to make it look like a wedding band.)
LOUISE: Do you love me?
Jimmy takes too long to respond yes, so Louise gets right back to business: "Wire it to the Western Union in Oklahoma City," she responds. Louise wants love and deep connection, but she's too smart to wait around for it or look for it where it won't appear. When Jimmy finally proposes, Louise knows years of the relationship not having worked won't equal years of it working perfectly, so she lets him down gently.
Over the course of the film, we see a bit of a role reversal: when Louise finally breaks down after having all her life savings stolen by some no-good sexy hitchhiker, it's Thelma who has to save the day. At this point, Louise has hit rock bottom. The can't-speak-anymore kind. It takes Thelma taking charge and suavely robbing a convenience store before Louise is herself again.
Brave, wise and true: that's Louise. No cliffhanger here...