Eva Mendes and Her Mini-Me 'Girl in Progress'

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Eva Mendes plays a single mom to Cierra Ramirez, a Girl in Progress, and the chummy co-stars tell ET that working together on the coming-of-age drama helped to create a special bond between them.

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"Sometimes I called her mini-me," says Eva of her teen co-star that plays her daughter. "I feel like Cierra's like a little sister to me, and I thought that was appropriate for the character, because I play such a mess of a mother in the film, so I thought, 'Okay, we'll go with this kind of sisterly thing.'"

In theaters this weekend just in time for Mother's Day, Girl in Progress finds Eva as Grace, a single mom who is too busy juggling work, bills -- and a relationship with the very married Dr. Harford (Matthew Modine) -- to give her daughter, Ansiedad (Cierra) the attention she desperately needs.

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When Ansiedad's English teacher, Ms. Armstrong (Patricia Arquette), introduces her students to classic coming-of-age stories, Ansiedad is inspired to skip adolescence and jump-start her life without mom. As mother and daughter clash over their difficult living situation, Ansiedad and Grace must learn that sometimes growing-up means acting your age.

"As a human you yearn to love and be loved in return, and that was just the main idea of [Ansiedad's] whole plan," says Cierra.