YOU SAID:

since that friend was an end in herself

INTO JAPANESE

その友人は自分自身の終わりだったので

BACK INTO ENGLISH

Because the friend was the end of himself

INTO JAPANESE

友達が自分の終わりだったから

BACK INTO ENGLISH

Because my friend was my end

INTO JAPANESE

私の友人が私の終わりだったので

BACK INTO ENGLISH

Because my friend was my end