Anne Hathaway has done spunky (“The Princess Diaries”), sexy (“Get Smart”) and bland (“The Devil Wears Prada”), but she’s never commandeered the screen like she does in “Rachel Getting Married.”

The new film also marks director Jonathan Demme’s return to respectable filmmaking after a protracted absence.

Yet “Rachel” turns indulgent in its final scenes and bludgeons us with a nonstop barrage of family dysfunction. Audiences should be handed a coupon for the nearest shrink upon exiting the theater.

“Rachel” casts Hathaway as Kym, a drug addict who essentially crashes her own sister’s wedding. The “Rachel” in question (Rosemarie DeWitt) is about to marry a man whose extended circle boasts a good dozen professional musicians.

More on that later.

Kym (Hathaway) is released from an addiction center as the story opens, and she heads straight for her old home where Rachel and family are prepping for the big day. The sisters’ father (Bill Irwin) is trying to keep his family intact for just … a few … more … hours, but it’s an effort that ultimately collapses.

Kym can’t beat back her demons for long, and reuniting with the picture-perfect Rachel reminds her of all her personal failings. And then there’s their mother, played with flinty determination by Debra Winger. The actress looks like the 53-year-old woman that she is, God bless her, and she makes the most of her modest screen time.

The wedding itself is an affair that goes on for what feels like a week. Maybe two.

Demme and screenwriter Jenny Lumet capture the family rhythms with an intimacy and attention to detail that draws us uncomfortably close. It’s why when the film switches into wedding mode “Rachel” flies off the rails.

The big event is like a Grateful Dead concert that just doesn’t know how, or when, to deliver the last encore.

Hathaway emerges unscathed, and she’ll likely snare an Oscar nomination for her troubles. Good for her. Roles like Kym often end up in the hands of greedy actors who lunge at every meltdown. Hathaway gives the young woman a vulnerability that isn’t conveyed by her actions or words.

It’s hard not to look away when Kym spins out of control time and again, but Hathaway makes it worth the effort to stare right at her.

“Rachel Getting Married” is as loud and out of control as the worst family reunion, but it reboots Demme’s career and puts Hathaway on a pedestal few thought she’d ever ascend.

(Photo: Can you feel the crazy? Anne Hathaway plays a recovering addict trying to stay clean, sober and sane during her sister’s nuptials in “Rachel Getting Married.”)

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