YOU SAID:
she decided to let the cat out of the bag
INTO JAPANESE
彼女は猫を袋から出すことにした
BACK INTO ENGLISH
She decided to take the cat out of the bag
INTO JAPANESE
彼女は猫を袋から取り出すことにしました
BACK INTO ENGLISH
She decided to take the cat out of the bag
That didn't even make that much sense in English.