Not character development, but concept(?) development. I honestly just wanted to share what I've thought of so far(what I can remember at least).

So, I remember saying in a rp(one I'm very ashamed of) that smelling the flower is harmless. Yeah, no. Not anymore. Now, the flower smells toxic, and it sends a signal to the brain that forces the airway(lungs) to close off temporarily. In other words it makes it difficult to breath for a bit.

I don't think it needs to be injected into the heart anymore, just a vein. I'm thinking the way the poison works is that it does something to blood cells, either replacing them or infecting them, might need help with that. It'll probably be replacing them though.

On the topic of the whole blood thing, since the poison is basically the blood, it's still pumped to the brain, which causes the side effects. The poison kills through suffocation(forcing the lungs to close). The poison and the smell basically send the same signals to the brain, except the poison is more severe.

Literally all I got so far. Dunno if this is enough development to try again with the story idea...