“I’ve been playing moms since ‘Training Day,’ and I was 25 when I made that,” Eva Mendes says. “Being a bad mom should come easily, by now.”

So don’t read too much into her role in “Girl in Progress,” Mendes’ latest film. The veteran spokesmodel, queen of men’s magazine covers, a woman who, onscreen, is adept at “keying into both male and female fantasies of womanhood” (Interview Magazine), may have just turned 38. That doesn’t mean she’s quite ready to transition into “mom” roles. Even if her character, “Grace,” a self-absorbed and immature mother of a teen (Cierra Ramirez) who needs her, is what Susan Sarandon likes to call “a mom…with legs.”

“‘A mom with legs,'” Mendes purrs. “I can work with that.”

“Girl in Progress,” from the director of “Under the Same Moon (La misma Luna)”, checks in the trainwreck of a life that Grace (Mendes) is leading, a struggling waitress and maid having an affair with a married man, and the trainwreck about to happen that is her daughter, whom Grace thoughtlessly named Ansiedad (Anxiety). Grace has made mistakes, and seems helpless to intervene when her very smart daughter sets out to pass several teen “rites of passage” that could put her on the same dead-end life course that mom followed.

“Grace is so human, so incredibly flawed. She seems like a real person, and did, even on the page. She’s trying her best, and failing. Miserably. She’s failing to be a ‘present’ mom, failing to be a stable influence on her daughter’s life.”

A favorite scene illustrating this? Mendes lit up for that one.

“I’m smoking in the car with the girls, my daughter and her friend, riding with me,” she says. “I’m smoking a real cigarette, and I’m kind of blowing smoke in their faces. That’s like the ultimate sign of a bad mom, kind of our ultimate taboo. When I was growing up, my family had its smokers. My parents had friends who smoked. And it wasn’t nearly the taboo it is now. That scene encapsulates Grace, and the movie. She’s not considerate, not necessarily smart, and not a mom who thinks things through. That’s her.”

But Mendes found redeeming qualities in her character, as actors are wont to do. She points out the sacrifices Grace makes to give Ansiedad a chance, and took her inspiration from a key movie of her own youth — “Stella,” the 1990 Bette Midler remake of that classic mother-daughter weeper, “Stella Dallas.”

“I’ve not seen that movie since i came out, but I remember it made a huge impression on me. HUGE. It reminded me of my relationship with my mother, the things she does that drive you crazy, the things you feel guilty about in the way you treat her.”

Mendes still isn’t letting on much about her own thoughts on motherhood (She’s been in a relationship with Ryan Gosling since last fall). And she’s still getting plenty of offers to play women who aren’t moms — she’s very high on the upcoming “The Place Beyond the Pines,” in which she co-stars with Gosling, a film by his “Blue Valentine” director, and the Cannes competition sci-fi fantasy “Holy Motors,” by Leos Carax, “a movie where I have a big role, and not one single line of dialogue! I love that. I’m trying to make all my movies more like that.”

But if there are mothers in her Hollywood future, Mendes is down with that. “Stella,” which she saw when she was 16, sticks with her.

“I’m a sucker for a good mother-daughter story.”

(Roger Moore’s review of “Girl in Progress:)

(Roger Moore’s review of the weird not-quite-wonderful “Holy Motors”)