Willis and Lohan at an American Cinematheque event in 2006
Rumer Willis, the oldest daughter of Bruce Willis and Demi Moore, says she's on pal Lindsay Lohan
's side as the actress deals with rehab
and DUI charges
"I haven't talked to her, but I wish her the best," Willis, 18, told PEOPLE at Thursday's BlackBerry Curve launch party in L.A. "I think there a lot of people that are supporting her. It's been kind of a crazy week, figuring it out, and figuring out a better way to be."
Lohan was charged with DUI after her Mercedes crashed in Beverly Hills around 5:30 Saturday morning. Police said they found a substance they believed to be cocaine in her car. Lohan checked into rehab on Monday.
Willis, who has been photographed around L.A. with Lohan, says the actress's age, 20, should be taken into consideration. "I think it's definitely hard growing up in L.A. with all of the things that you have to deal with, and being so young," Willis said. "I think sometimes people don't realize the amount of pressure that can come."
Willis also said she approves of another friend in Lohan's life, DJ Samantha Ronson, who was photographed over the weekend driving an apparently passed out
Lohan – and who has also been named by Lohan's father, Michael, as a bad influence.
"She's great, she's a really cool person," Willis said of Ronson. "She doesn't give a crap about what anybody else thinks about her, which I really respect."