Lindsay Lohan: Lighter Locks!

Lindsay Lohan sips on some coke as she makes her way back to her car after shopping at the Arcade Store in West Hollywood on Monday (August 10).

The 23-year-old Mean Girls actress spent the weekend with on-again girlfriend Samantha Ronson in Chicago to go to Lollapalooza and celebrate Sam‘s 32nd birthday.

Lindsay and Sam sat side-by-side throughout the meal at Hub 51, where they were joined by friends and family. “They kept smiling at each other and holding hands,” a source told Star. “It was very sweet. Not only did Lindsay make a toast to Sam, but because Lindsay was so caught up in the moment, she Twittered a special message to Sam to let her know how happy she was.”

25+ pictures inside of Lindsay Lohan‘s lighter locks…