It really shows on your face when you don't like someone. You should be more careful.
It's so noticeable when you don't like someone. You should try to hide your feelings a bit more.
この場合、次のような言い方ができるかと思います。
ーIt really shows on your face when you don't like someone. You should be more careful.
「あなたは嫌いな人がいると顔にすごく現れるね。気をつけたほうがいいよ」
to show on one's face で「顔に表す・顔にはっきり出す」
ーIt's so noticeable when you don't like someone. You should try to hide your feelings a bit more.
「あなたは嫌いな人がいるとすぐわかるね。もうちょっと感情を隠したほうがいいよ」
noticeable で「容易に気づく・目立つ」
to hide one's feelings で「感情を隠す」
ご参考まで!