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What Mei says out of the bubbles in the first panel is
カタカタカタカタターンとな
The カタカタカタカタターン is supposed to be the clicking of a keyboard, with the ターン being a especially hard click done in a 'cool' way. You have probably seen it in media before, where some character finishes something important and ends it with an exaggerated arm movement.
The とな seems to be a way to ask for confirmation of what was said. It might be Internet slang? I'm not really sure. I think it is like ending a sentence with "you know?" in English.
(I don't actually know Japanese, I just did a bunch of Googling.)