London: Socialite Paris Hilton sympathises with her friend Brooke Mueller, estranged wife of Charlie Sheen, who is struggling to overcome substance abuse problems.
Mueller was filming for Hilton`s new reality show "The World According to Paris" at the time and the hotel heiress admits it was difficult to watch her friend suffer.
"You know, it was a lot of things going on during that whole Charlie thing during the show and I think she was going through a lot," Hilton said on "The Tonight Show" with Jay Leno.
Mueller has turned to professionals to help her.
"Right now she`s in treatment and I`m wishing her the best. She`s going through a lot. It has (been hard to see). It`s definitely been something that she has been struggling with since her teen years and it`s a daily struggle," said Hilton.