Ruth Westheimer—all four feet, seven inches of her—sat down at a restaurant booth the other day and took out her handbag. “I brought you something,” she said, plunging a hand inside. “Wait, wait, wait—someplace it’s here.” Out came a bag of sucking candies. Frustration. “Not with the candy.” Ah, there they were: Dr. Ruth produced two “Sex for Dummies” key chains. “It’s out in twenty-seven languages, the ‘Sex for Dummies,’ ” the book’s author explained. “It’s now out in Turkish, which really surprised me, because, after all, it’s a Muslim country.”

Westheimer, who is eighty-five, had just come from a performance of “Becoming Dr. Ruth,” an Off Broadway play (she prefers “Near Broadway”) by Mark St. Germain that chronicles her eventful life: Holocaust survivor (she was born in Germany and sent to a Swiss children’s home by her parents, who were killed by the Nazis); soldier (she fought in the 1948 Arab-Israeli war); sex therapist (her radio show, “Sexually Speaking,” began in 1980); and grandma. “I’ve seen it now fifteen times at least, maybe more,” she said of the show. “I sit purposely on Row K—that’s for Karola, my name that I had in Frankfurt.” What is it like to see your life story onstage? She shrugged. “Somebody said to me, ‘It has to be like an onion that you peel.’ And I said, ‘You peel your onions for yourself! I’m not an onion.’ ”

In “Becoming Dr. Ruth,” she is played by Debra Jo Rupp (the mother in “That ’70s Show”), who joined her at the restaurant. During rehearsals, Westheimer gave Rupp pointers on how to look and act like her. “Everybody thinks they know what Dr. Ruth sounds like, and everybody’s idea is different,” Rupp said. Certain words were hard to pronounce, especially “Barbara” (Westheimer’s daughter-in-law) and “Stehaufmännchen” (a type of German doll). Then there was the physicality. “We had lunch one day, and I said, ‘O.K., here’s the thing: you are always sitting. I need you to walk.’ And I brought my camcorder and I had her walk—back and forth, back and forth,” Rupp said. “Short people, I have decided, march. They just march. Because they have to go so fast just to keep up with everybody else.”

Part of what attracted her to the role, Rupp said, was a little-known fact: Dr. Ruth was a trained sniper. “Not an act of heroism,” Westheimer clarified. “In 1947 and ’48, everybody in then-Palestine belonged to some group. I chose the group that was the forerunner of the Israel Defense Forces. And I did not know that I had good aim. So when they did some selection, whatever, they put me in a group and they taught me how to put the Sten gun together. I shot the sky very nicely with my eyes closed.” Fortunately, she never had to put her skills to use. “I have no idea what the experience would be, if I had to show it. But I was a very good sniper. I could put the five bullets in the red circle. And I know how to throw hand grenades.”

In the play, a photo is shown of Westheimer’s sniper years. “I really studied that,” Rupp said—far from the exuberant bubbe we know today. “There’s a lesson in the Talmud,” Westheimer pronounced, her head barely clearing the table. “It says, ‘A lesson taught with humor is a lesson retained.’ ”