After everything came out about Thomas [Matthew Atkinson] and she saw his true colors, Carter was right there for her. He didn't say 'I told you so.' He was just there for her, and that stood out. It's like, 'Wow. He doesn't need validation. He's just a good guy.'
But what changes everything for Zoe, Barnes revealed, is seeing hunky Carter shirtless! She teased:
Well, of course, Zoe recognizes a handsome, good-looking guy when she sees him. But it does catch her off-guard when she's in an office looking at papers and comes in and catches Carter shirtless. It's like, 'Oh, this is not business-oriented.' But it is a fun, cheeky moment between the two--and it's obvious there is an attraction between them.