The Bodyguard

Saint Mercy, the bodyguard of crime lord and self styled Count of the Deadlands, Darius Trace.

Count Darius is a humanoid reptilian vampire and Mercy is a pure human,but that doesn't stop them from having a "close" relationship. These are not psychologically healthy people.

As well as being a bodyguard she's also a bounty hunter and acts as a law enforcer, this usually involves shooting people that The Count doesn't like.

After Ulrik Richter and his gang break into the Count's Stronghold to rescue Alice, Saint Mercy and a bunch of mercenaries are sent out to deal with them. No one breaks into the Count's home and gets away with it.