I had Vanessa Jeong (still a one star celebrity with the Brushes with Fame quirk) develop the Far from Greatness negative moodlet while at Orchid A Go Go. Having Throne Bailey (4 star celebrity) mentor her on guitar did not clear the moodlet, nor did performing a romantic scene with him. Getting to know him after the romantic scene, however, did. This is with mods disabled, and version 1.113.277.1030 DX11 on PC, English, and all expansion, game, and stuff packs.
Being mentored by a celebrity of equal or higher fame level, or performing an acting scene with them, should in my opinion fulfill the need to socialize with other celebrities that comes with the Brushes with Fame quirk.