testimony got under way in murder trial of 24-year-old shayna hubers accused of killing ohio lawyer ryan poston in 2012 .
jurors were shown videotaped police interview with hubers , where she claimed she shot poston in self-defense .
hubers , then 21 , told police she shot poston in the face and then fired again to put him out of his misery .
hubers described poston was ` vain ' to detectives and said she gave him the ` nose job he wanted ' by shooting him in the face .
woman told police how poston allegedly pushed and shoved her , and mocked her for being a ` hillbilly from kentucky '