Fiona was looking at him with wider eyes. People expect you to be honest, but it's not necessary that everyone likes honesty. Most of the time people prefer lies, they want others to lie because it's comforting for them.
They wanted you to tell the truth that they have already considered as truth. But Fiona was not one of them, she likes his honesty, and she smiles over what he said.
"You just seem scared to get attached to someone," Fiona said flirtatiously.
"What? Why would I be scared of getting attached now? Aren't I already attached to you?" Winston said while trying to convince her with an intense look.
"Yeah, but kids are different," she said looking into his eyes.
"How? And how do you know that? You don't have any kids" he said instantly.
"Because I am a woman and I just know these things," she said, taking her head away from his arm.
"What? It doesn't make you right though" he said with wide eyes.