YOU SAID:

She is a party pooper.

INTO JAPANESE

彼女はパーティーの愚痴者です。

BACK INTO ENGLISH

She is a party complainer.

INTO JAPANESE

彼女は党の不平を言う人です。

BACK INTO ENGLISH

She is the one who complains about the party.

INTO JAPANESE

彼女は党について不平を言う人です。

BACK INTO ENGLISH

She is the one who complains about the party.