Alicia Silverstone has her best big screen role in ages in “Sister of the Groom,” a “big fat Jewish wedding” comedy in which she has the title role, but which she apparently had to soldier through in the last stages of laryngitis.

She plays Audrey, just turning 40, proud mother of twins, still so embittered by the stomach they left her with ten years before. The mere touch of her round, stretch-marked belly by husband Ethan (Tom Everett Scott) makes her recoil and shriek.

“I HATE MY BODY!”

She’s struggling to relaunch herself as an architect — the career she never quite got off the ground before the babies came. And now she’s got to pour her 40-year-old body into a dress that flatters her for her brothers’ wedding, moved up to fall on “Jewish Valentine’s Day,” the “Holiday of Soulmates.”

She’ll meet rich-developer little brother Liam’s French bride-to-be. Clemence (Mathilde Ollivier) is a willowy, vain demanding pop-star-in-the-making. Liam (Jake Hoffman) is utterly in her thrall, and that’s bound to rub Audrey the wrong way in this wedding at their family’s old home on Long Island, which Liam bought and plans to live in after the wedding, after renovations.

Husband Ethan and Audrey’s dad (Mark Blum) keep the piece as the French folk — Ronald Guttman is father of the bride — prove to be a bit rude, a tad coarse, and unapologetically demanding. There are Israelis on that side of the family, too. Thus, an Israeli rabbi has been flown in.

The house their late mother adored will be renovated, but not via Audrey’s submitted plans.

“We’re thinking, it’s better not working with family.”

As the slights cross into humiliations and the insults spread from the challah to the chuppah, Audrey and Clemence cross the line from putdowns and testy exchanges to open warfare.

The situations set us up for a funnier movie than Amy Miller Gross gets out of this material. Old flames, drugs, ruined dresses all rude new in-laws piled on top of “This is 40” take-stock moments should have produced more laughs. There aren’t a lot of overtly Jewish wedding comedies, so novelty works in Gross’s favor, just not enough.

The assorted heart-to-hearts play well, and Silverstone still shows some (limited) comic chops. But there’s no flow, no scene-topping-scene build-up of laughs, heart, etc.

Having characters watch “My Best Friend’s Wedding” at one point isn’t helpful. Leaving the sole profundity expressed here to die of loneliness is a sin.

“It’s the people who trigger us most who are our greatest teachers.”

Write this one off as a “nice try,” and too bad about the laryngitis Ms. Silverstone.

MPA Rating: R for language, drug use, some sexual content and brief nudity

Cast: Alicia Silverstone, Tom Everett Scott, Mathilde Ollivier, Mark Blum, Jake Hoffman, Ronald Guttman, Julie Engelbrecht, Noah Silver and Charlie Bewley

Credits: Scripted and directed by Amy Miller Gross. A Saban Films release.

Running time: 1:32