Loki did frown toward the door when nothing happened. While he hadn't found it as unpleasant as Sif perhaps had, he had expected that may be what they had to do.

With that in mind, he decided something had to be reciprocated. He had been too startled by her boldness so maybe that was the problem...

So he moved in and closer, his hand going to her cheek to keep her still - if he could - and gave her a kiss back. It wasn't passionate but neither was it chaste.