Well, I would think it would be quite obvious if he likes her. He might play with her, chatter with her, etc.
What you should be worried about is any aggresion such as biting that shows up between the two.
I'm growing basil plants. And I want to give a little bit of the leaves for my little ones to try and eat. How long should I leave the basil leaves in? Can they be left for a long time> Or only a few hours.