Lindsay Lohan a thief?

"Lindsay stole $10,000 worth of clothes and accessories from one of her former friends, Lauren Hastings, and has absolutely no shame about it. In fact, she even laughed about it with her girlfriends, among them Nicole Richie and DJ Samantha Ronson."

On Sunday night, April 15, Lindsay visited Lauren's home in Los Angeles, which at the time was being watched over by a mutual friend because Lauren, a model, was working on a shoot in Texas. According to the source, Lindsay told Lauren's house sitter that she had left some of her clothes at the house and needed to pick them up. The house sitter, a mutual friend to Lauren and Lindsay, saw no reason Lindsay would lie about such a thing, and so she let the starlet inside!

But Lohan, whose normally chummy relationship with Lauren recently turned sour, scurried into her former pal's bedroom, her bodyguard tagging along, and gathered up huge armfuls of clothes, purses and belts, a source tells Star. Almost everything was expensive, designer items, things Hastings picked up on various modeling shoots or bought at high-end designer stores. In all, the source says Lindsay and her bodyguard left with an estimated $10,000 in merchandise, which she ordered her security man to load into her car.

"The mutual friend saw Lindsay leaving with everything, but she just didn't think that Lindsay would actually be lying about the clothes and steal their friend's things! At the time, she was under the impression that Lindsay and Lauren were still friends! That is, until Lauren came home the following day and flipped out. She started yelling, 'Where are all of my clothes? Where are my things?'"

That Monday night, April 16, a sobbing Lauren went to a friend's house for support and decided to text message Lindsay, demanding all her things be returned. That's when a text messaging war broke out between the ladies. "It was nasty," describes a source who has read the text message exchange.

"Lauren sent Lindsay a text message threatening to go to the police and press charges," a source said.

Friends were out clubbing with Lindsay when she got the messages and at least one Lohan pal said the starlet responded by laughing uproariously. "Lindsay just told her she was delusional and claimed Lauren didn't know what she was talking about. She insisted the items weren't stolen because they did belong to her. Then she'd laughed to her friends about it. She thought the whole thing was hysterical," a source said.

Lindsay was at the nightclub Hyde in L.A. at the time, sitting next to friends Nicole Richie and famed-DJ Samantha Ronson, and began passing around her Blackberry to show off the exchange, causing the girls to burst out in laughter.

Lindsay texted Lauren that she was a fat bitch, a friend of Lauren's says. Nicole Richie also chimed in, a source said, and told Lauren that Lindsay would return the clothes after they cut them up!

"Nicole wrote that she and Lindsay were going to cut holes in Lauren's jeans because Lauren was so fat and her jeans didn't fit," our source notes. "Then Nicole told Lauren that if she went to the cops, she would regret it!" our insider said.

Lindsay's rep, Leslie Sloane calls the report "totally untrue."