YOU SAID:
Hello, I didn't realize you were so pretty
INTO JAPANESE
こんにちは、私はあなたがとてもきれいだとは知らなかった
BACK INTO ENGLISH
hi i didn't know you were so pretty
INTO JAPANESE
こんにちは、あなたがとてもきれいだとは知りませんでした
BACK INTO ENGLISH
hi i didn't know you were so pretty
That didn't even make that much sense in English.