This is a slang term which has no translation in Spanish. You
could describe the concept to a Spaniard as "una persona que
comporta como si fuera un amigo pero te traciona porque es un
enemigo" - "a person who behaves as if they were a friend, but
betrays you because he is an enemy".
The word for friend is "amigo" and the word for enemy is
"enemigo", so there is no way to combine the words liked "friend"
and "enemy" can be combined.