Can I say "what is this" instead?
No, it would not be correct grammar to say "what is this" here. This is because she is not specifically asking what the video is. She already knows what the video is and she is asking everyone else if they know what it is. If "this" is put at the end of the sentence, it would be incorrect and would change the meaning of the sentence. Ex: What is this plant? Ex: It's a flower, that's what it is.
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