I find it hilarious how the others don't understand what she's talking about half the time. XD And with the random Kamina cosplayer she's like "how nice to meet a living Kamina-san!" and says "I'm sorry" to him after she quotes the "Who exactly is Aniki-san?" line.
Fun info for Nia fans, some of which has been revealed in interviews before, but some is new:
-Fukui grew up in the countryside and considers herself naive
-She thinks of GAINAX as a father figure
-She was brought in to play Nia without reading the script first, so she could relate with not knowing anything about the world or other characters
-To get into Nia's character, she went to visit a field of flowers
-She actually synchronized too much with Nia, to the point that she came down with the measles when Nia turned Anti-Spiral, only to get better when Nia returned to the Gurren Brigade
Starting around 7:20, she says a couple of Nia's lines while in cosplay. "Gokigenyou!" and "If my father tells you to die, will you die?"
Starting at 3:24, they show some American Gurren Lagann cosplayers! :O lady_ava, you've just been complimented by Nia's seiyuu!!! Also unrelated, but omgyay she loves Princess Tutu!
The credits say "in cooperation with Cosplay.com" so they probably got the pictures from here:
Lady Ava's Messenger Nia
Noble Knight's Kamina