"Isn't this a second concert because something happened at the first one they did?" She won't specifically mention how she knows that from what they had told her -- Marinette. Even if it is probably obvious it is her.

I'm Ladybug. And this...well. It's what I wear when my kwami transforms me. It's easy to move around in at least."

Which is the important thing. Very necessary with all her running and jumping and dodging attacks from akuma victims and all. Though right after she says that, she might debate if that might be too much.