Pretty much what I was saying. Poison to weaken the heart then a trigger. Once that failed more poison but ended up killing her. Most likely the same poison in AC system. My wild guess is on arsenic. MOO.I've been trying to figure out the paintball incident because I think TD must have known it was a paintball gun specifically, and not a real gun. And "scaring" someone to death is barely a real thing so I'd brushed that off.... but what if they were "feeding" her something to weaken her heart and were hoping that it would be enough to actually scare her to death? And when that didn't work they switched to plan B (some sort of acute poisoning). Maybe that is what you were implying but the pieces just fell together for me! Time for more research!
Edit: words, clarity