YOU SAID:

I get a cat if my sister thinks I'm stupid.

INTO JAPANESE

妹が私を愚かだと思ったら猫を手に入れる。

BACK INTO ENGLISH

If my sister thinks I'm stupid, she gets a cat.

INTO JAPANESE

私の妹が私を愚かだと思うなら、彼女は猫を手に入れます。

BACK INTO ENGLISH

If my sister thinks I'm stupid, she gets a cat.