I actually love the idea that Namie went to Ayu's tour!
I think it's great that artistes show appreciation for each other's works! I mean even as a musical artiste, they have their own music preferences and styles, so I think it's healthy.
C'mon, you can't BAR people from going from the concerts of others. I'm pretty sure Ayu herself would like to attend some concerts, but her busy schedule doesn't allow for it.