Faithful, for any relationship to work be it a friend, coworker, team member, or that special someone, love demands being faithful (remaining loyal and steadfast) loyalty (a strong feeling of support or allegiance). To put it simply, love does no harm (cheat, backstab, talk bad, etc…) to others. 
Romans 13:10 (NKJV): 10 Love does no harm to a neighbor; therefore love is the fulfillment of the law.