Okay, but guys lets think about things a little bit, shall we?
Dean was still at the house when Nora arrived home at the end of the episode, She didn’t seem mad or put off by the whole ‘strange man in my house’ thing which means she had to come up with a logical explanation as to why Dean was there. I mean Cas kind of explains it, Dean knew how to bring the baby’s fever down, but he didn’t need to physically come to the house in order to tell that to Cas.
SO, I propose, that after seeing Dean and Cas together there’s no way Nora wouldn’t have picked up on the ex-lover vibes they were giving off all episode.
I think Nora thought Cas was gay, like right from the start. It would explain why she kissed him so casually and didn’t think anything of it and it would explain why she asked him in babysit in such a confusing way. She didn’t expect Cas to be interested in her so her wording was like she was speaking to someone who knew what she was talking about from experience – ‘it’s so hard to meet a good guy’.
Seeing Dean and Cas together, even if they were acting like exes that were seeing each other again for the first time after the break up, their connection would’ve been obvious and just confirmed what she thought.