The 25-year-old attended the dinner in Washington DC on Saturday night with her lawyer Shawn Chapman Holley, reported Femalefirst online.
During a visit to the ladies' room, Lohan met an elderly Hispanic cleaner Bianca and after seeing how hard she was working, she felt sorry for her.
"You are too old to be doing this," said Lohan. The "Freaky Friday" actress then reached into her purse and handed Bianca a USD 100 bill. The attendant initially refused Lindsay's generosity and said, "No, no, no."
Other guests at the dinner included Kim Kardashian and her mother Kris Jenner, Elle MacPherson, Josh Hutcherson, Mary J Blige, Goldie Hawn and Eva Longoria.