The actress, 33, and contemporary artist Yellin first caused a buzz when they stepped out holding hands following Williams' solo appearance at the Metropolitan Museum of Art's Costume Institute Gala in New York City back in May 2013. Ironically enough, the Dawson's Creek alum walked the red carpet yet again without a plus one at the 2014 Met Gala on Monday, May 5.
Williams, for her part, kept her relationship with the hipster, 38, extremely tight-lipped. One of the very few times they were photographed together was back in June taking a walk in the rain in Brooklyn.
Williams is currently starring as Sally Bowles in Broadway's Cabaret in NYC. The cast and crew celebrated their opening night late last month, a gathering Yellin didn't appear to attend. Williams' Dawson's Creek former costar Busy Philipps, however, did support her best friend during a May 2 showing.
"I am so proud. I can't stand it," the Cougar Town actress, 34, gushed via Instagram, along with a snapshot of the pair. "You need to go see Cabaret if you're in New York because MY BEST FRIEND KILLED IT."
Williams previously dated actor Jason Segel, 34, for nearly a year before their split in February 2013. As sources told Us, distance was ultimately to blame. (Williams and Matilda, her 8-year-old daughter with her late ex Heath Ledger, reside in Brooklyn. The How I Met Your Mother alum lives in L.A.)
That April, the mom told Paper magazine that Matilda was her first priority. "Raising the kid is the work, yeah. And it's amazing, and it's the ultimate creative act," Williams said. "That's my side project and my center project."