I think it’s unlikely that they met again because Zira would have kept Kovu under strict watch and been busy training him. Although Kiara has no problem slipping away from her babysitters, it would be difficult for her to arrange a meeting with Kovu. It’s not like she would be able to send him an SMS.
That being said, I do believe they met several times after their first encounter. I think they both were fascinated by eachother, and Kovu especially really wanted them to be friends. Also, I think Kiara seemed very lonely as a cub, so I don’t think she would let a chance at befriending another cub slip away.
In short: I believe they could have had a few, sporadical meetings. I think Kovu made quite an impression on Kiara at their first meeting, it was his innocent question "what are you doing?" that made her recognize him when they met again as adults.

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