Samantha Ronson and Lindsay Lohan at China Grill
Seth Browarnik/Red Eye Productions
08/04/2008 AT 11:30 AM EDT
and girlfriend Samantha Ronson didn't hide their affection as they spent the weekend rocking out in Chicago.
The couple was in town for Lollapalooza, Chicago's annual three-day music festival, which also drew Pete Wentz
and Ashlee Simpson to town
Mixing some work with play, Ronson was spinning at Crimson Friday – with Lohan in tow – before they hit Underground that night. The duo hung out at the the MOTOROKR Lounge at Underground with Danny Masterson and singer Kenna before settling into a table for the night. "They were holding hands and very affectionate with each other," says an onlooker. Samantha's brother Mark Ronson was the club's deejay.
The next night, they joined Mark and his girlfriend at China Grill Chicago for Diesel's Rock The Vote Private Dinner. "They were very comfortable, very touchy-feely," says a source, who added that Lindsay looked "great." "They were holding hands the entire night. They weren't hiding anything."
While feasting on drunken chicken and veggie fried rice, the ladies took frequent cigarette breaks and greeted fans as they smoked outside. "They were very gracious," the source said. "They signed autographs and took pictures with kids."
By the end of the night, the source said, one thing was clear: "They're in love. This is a no-joke deal."
After dinner, the group headed to The Music Lounge at the Hard Rock Hotel, where Samantha was back at the turntables. When Mark deejayed, the girls texted back and forth and danced onstage to the last song.
The pair spent the previous week getting cozy
in New York before flying to Los Angeles
Reporting by KIM PEIFFER and AIXA VELEZ