Imagine you go into your kitchen at night, turn on the lights and there's a filthy cockroach on the floor. What do you do? You squash it. You don't even think about it, you acknowledge the filthiness of the cockroach, and kill it without hesitation.
Riven is similar, however the cockroach is actually an important part of the ecosystem, putting her below the cockroach. She's worthless and disgusting, dying is the best thing she could ever do for the world, and not a single person would mourn her loss (except for the cockroaches who no longer have anyone to make themselves look good).