She has to know he regrets ever looking at her with fear let alone any more skepticism than she deserved. Her persistence is her best trait and it is only natural she won him over eventually.

He underestimates himself sometimes only because his mind never ceases to think; she helps the thoughts melt away more easily with the look of a cat with a canary in its sights though. He won't necessarily do the best job on the sigil but his attention on completing it is fair enough. It comes out legible enough that the lines and grooves are correct and the magic accepts it as the final link. Right before their eyes it disappears into the wall.

It's hard to forget that they're married on a technicality. Her calling him Mr. Winchester causes his heart squeeze in his chest and pulse to race a little higher. He needn't any (further) encouragement to go where she's going with this. "Mrs. Winchester...I might have a few ideas." Sex is obviously the end goal. But there's a number of things they've tried in the last month that could test the noise boundary.