She couldn't help it. She giggled at him. She knew that wasn't how his mind worked, but it was such fun to make it go that direction, and watch it make him turn colors. It was some twisted kick of hers. She was giggling softly now. And ruffling his hair lightly.

"I'm sorry, koi. Sometimes, you're just so fun to tease." She doesn't sound precisely apologetic that she'd made him blush, more apologetic that she got such a kick out of tormenting him this way. Sure enough it didn't mean she'd stop.