>>43507164The feel valid thing pertains to something she said earlier, Nina much like Kiara has had a ton of shit tossed her way, she doubted herself a lot, felt she didn't belong, considered quitting, but seeing merch of herself and her senpais made her realize she's part of something bigger than herself.
She really wants to get better at singing and do concerts and other things, I'm guessing the valid compliment was due to that, IE, keep following your dreams.