YOU SAID:

she told me that he told her that he cheated on me

INTO JAPANESE

彼女は彼が私をだましたと彼女に言ったと私に言った

BACK INTO ENGLISH

She told me he told her he cheated me

INTO JAPANESE

彼女は私に彼が私をだましたと言ったと言った

BACK INTO ENGLISH

She told me he said he cheated me

INTO JAPANESE

彼女は彼が私をだましたと言ったと私に言った

BACK INTO ENGLISH

She told me he said he cheated me