Ashlee Simpson-Wentz Partying, Drinking Days Before Split

 Jordan Strauss/WireImage.com

Ashlee Simpson-Wentz sure wasn't feeling down last Friday, Feb. 4. Five days before she filed for divorce from Pete Wentz after less than three years of marriage, the star, 26, was out on the town in Hollywood — hitting SHG's Eden nightclub.

Arriving around 1 a.m. with three girlfriends, Simpson-Wentz kept it casual in a faded rock t-shirt, leopard print overcoat and black pants. The singer-actress and her gal-pals watched a live performance of "Mini Gaga" and "Mini Beyonce" — and kept the cocktails flowing, a witness tells Us.

"She was drinking Grey Goose and Sugar-Free Red Bull all night," the witness says. "She was laughing a ton," adds the Eden observer. "She didn't care who was around her…she was just there to have fun."

Things were less festive by Wednesday, when she and Fall Out Boy rocker Wentz, 31, confirmed their decision to divorce. "We remain friends and deeply committed and loving parents to our son Bronx, whose happiness and well-being remains our number one priority," they said in a statement. (Their little boy is 2 years old.)

And although many were shocked by the divorce news, one source close to the couple tells UsMagazine.com the young pair have been headed for divorce "for quite some time."

At issue, among other things: Ashlee's "partying [and] being out of control," the source says.

Indeed, way back in June 2009 — just 13 months into their marriage — Simpson-Wentz was already "reverting to drinking and going out," another pal told Us Weekly at the time. The wild behavior was "an outlet for her unhappiness," the pal explained.

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