"I adore him," Barrymore, who wore a retro flesh-tone Alberta Feretti gown to the premiere of her HBO movie Grey Gardens, said of Long. "And I thank God that my friend supports me the way he does."
The off-again, on-again pair were affectionate the night of the premiere Tuesday. During the screening, she leaned over her seat to give him a quick smooch. At the movie's after-party at the Pierre hotel, Long, 30, and Barrymore, 34, posed for photos together. Later inside the hotel, she dragged Long into the dining room while holding his hand and gave him a long embrace, whispering into his ear.
Letters from the SetMichael Suscy, who directed Grey Gardens, told PEOPLE that during the filming of the movie Barrymore "would correspond with [Justin], but only by writing letters on a typewriter – no modern technology, only technology that her character, Little Edie would have had."
Barrymore – who was also recently spotted with another ex-boyfriend, rocker Fabrizio Moretti – said the old-fashioned letters, which she wrote on an avocado green IBM Selectric typewriter, helped her work through her jitters about the part. "Thank God for him because he was my wonderful outlet, my dear friend throughout the process ... I had to understand what isolation was really like."
As for the subject of the letters, "They were about my fears of not being able to pull this character off, this icon, about learning a level of discipline ... about facing your fears," she said.
According to Long, Barrymore had nothing to worry about. "I'm so proud and stunned. It's unbelievable. She lost herself completely. It's an amazing, beautiful, transformative performance. She's one of the greats."
As for their future, Barrymore is looking forward to more laughs with Long. "We're doing a movie together this summer. We're doing a comedy. It's so much fun. I can't wait to get back into comedy," she said.