The Olsen twins are telling friends they’ve toned down their partying ways since the death of their friend Heath Ledger. As Ashley and Mary-Kate prepare to celebrate their 24th birthday next month, a source said of the former Bungalow 8 fixtures that although neither used drugs, “It was a sad wake-up call for both of them. They’re doing very well with their clothing lines.” The girls sat with Ashley’s boyfriend Justin Bartha‘s mom at the party for his movie “Holy Rollers” at Avenue the other night.