not know which end is up

Verb

idiomatic

(idiomatic) To have no common sense; to be ignorant of the most basic facts; to be very confused.

Japanese Meaning

常識がなく、基本的な事実さえ理解できずに混乱している状態を表す表現です。 / とても無知で、最も基本的な知識を持っていないことを示す表現です。

She seems to not know which end is up when she's asked to make basic decisions.

彼女は基本的な判断を求められると常識がないように見える。

Sense（1）

(idiomatic) To have no common sense; to be ignorant of the most basic facts; to be very confused.

“I'm not some naïve, virginal little nothing who doesn't know which end is up.”