"Me and the fabulous Michael Costello at the SOAR Los Angeles Gala!" Bynes Tweeted Tuesday night, her first post since sharing what appeared to be a self-portrait sketch in March
Credit: Courtesy Amanda Bynes

Amanda Bynes returned to Twitter for the first time since March on Tuesday, sharing a photo of herself with designer Michael Costello at a Los Angeles gala.

“Me and the fabulous Michael Costello (I’m wearing one of his beautiful gowns) at the SOAR Los Angeles Gala!” Bynes Tweeted Tuesday night, her first since posting what appeared to be a self-portrait sketch in March.

The photo, taken at The Society for Orphaned Armenian Relief‘s Casino Royale-themed black-tie event Sunday night, captured a smiling Bynes, 29, with long blond hair and a black dress. Bynes hugged the designer, who was sporting a polka-dot black-and-white bow tie.

“She was 100 percent in good spirits – she’s just a sweetheart,” the gala’s event planner, Kat Minassi, told PEOPLE of Bynes, who wore a dress by Costello. “She had a wonderful time. Amanda supports the cause as well, so she came out with Michael for the evening and she was in great spirits. She enjoyed the evening with us and looked beautiful in her gown.”

With the help of Costello and his designs, the event raised over $60,000 for Armenian orphans worldwide.

The Project Runway alum also posted an Instagram pic of Bynes wearing a white dress with Jesse Castell, Costello’s boyfriend. The photo appeared to be taken in July when the former child star made a surprise appearance at the launch of the fashion designer’s pre-fall capsule collection in Los Angeles.

“@jessecastell and Amanda Bynes at our @houseofborel @stylepr event #amandabynes,” Costello tagged the picture.

The designer told PEOPLE in July that Bynes – who has attended fashion school, herself, at L.A.’s Fashion Institute of Design & Merchandising – was “the biggest Michael Costello fan,” and the two seem to becoming fast friends.

Previously, Bynes was last spotted in public in June, having lunch in West Hollywood with her life coach.

Her attorney told PEOPLE that the actress was “doing great.”

In October 2014, Bynes was treated in a psychiatric facility following a 2012 DUI arrest, a shoplifting incident and a series of Tweets in which she lashed out at her parents. She was also involuntarily hospitalized in July 2013.

The Nickelodeon alum remains under the temporary conservatorship of her parents and had previously been scheduled for a June 23 court hearing to assess her condition.