Lindsay Lohan leaving a medical building in Beverly Hills (3/18)

Surprise, surprise, Lindsay Lohan and Sam Ronson got into yet another huge fight last weekend at Prive nightclub in Las Vegas. A witness told In Touch Weekly:

"They would argue every five minutes," the onlooker says. "I definitely heard Lindsay use the 'F' word." When Sam finished her gig, she ran out of the club — reportedly pausing to throw up behind a curtain — then jumped in her Porsche and sped off, leaving an irate Lindsay behind. "Lindsay was screaming and cursing at Sam to stop," the witness adds. "She made a huge scene."

Sam's family has finally had enough -- they want her to ditch Lohan:

Although Sam denied on her blog that she got sick, Lindsay’s increasingly volatile behavior has taken a toll on Sam, physically and emotionally, and her family is worried.

"They totally disapprove of Lindsay. They think she’s a bad influence," an insider reveals. "They’ve urged Sam to get out of the relationship. Everyone knows she isn’t happy living like this, but she won’t leave Lindsay. She can't. Sam feels too guilty to leave, so she stays. But the relationship is completely crazy."

When the family of an anorexic lesbian DJ thinks you're a bad influence, it might be time to reevaluate your life. The fact that Sam won't leave Lindsay has nothing to do with guilt, and everything to do with money. If Sam broke off their relationship, she'd be just another has-been loser whose only claim to fame was once banging someone famous. So a lot like Courtney Love . . . and my left hand.

[WENN]