I've taught communication skills for people who deal with clients who are describing problems in their life, and taught about how to empathise or sympathise with them. I also have plenty of friends who are psychiatrists and counsellors, and for a nervous child, telling a story which makes them laugh and feel more comfortable about what they're saying, is absolutely what I'd expect someone to do if they're trying to show an interest.
The clip is headlined with the quote about 'treats', which she doesn't even say till the end, so we don't get to see what he actually says. He may be picking up on her body language, but then given it's a clear photo op, and the kid is being prompted by her mum, my cynical side would suggest that he knows full well she's not finished asking her question.