He wasn't sure of the best course of action at that point. Ask about his niece or drop the subject? See what her future was like or talk about the present? While not normally the cowardly sort JR couldn't stand seeing his little sisters upset, and there didn't seem to be anything he could do to fix the problem in this particular case.
"Have your food before it gets cold," he urged, deciding to let her tell him what she wanted to talk about if anything at all.