They may not see other family members as criminals. I believe they saw her as someone who comes in and takes advantage of their elderly relative by seducing him. They doubtlessly see her as a thief who was trying to steal their family fortune. I have no idea whether or not they had a hand in anyone's death, and I don't pretend to. I was just saying they had one hell of a motive, and the order of the deaths is how they would want it done.
I agree. The fact that she'd already had a reputation as a drug user makes "getting away with it" a slam-dunk.