Time Traveler

"She just substituted one letter for another. She said to write the keyword out and then the rest of the letters of the alphabet after that. Write that again below the first alphabet and slide it over. I didn't really understand."

"You mean something like this?" I ask and write this on his paper.

KEYWORDABCFGHIJLMNPQSTUVXZ (plaintext)
QSTUVXZKEYWORDABCFGHIJLMNP (ciphertext)

"Yes! Exactly like that. But with a different key."