It's me.
Ok let's take Plumeria and Blanc out:
Cain
prettiestofflowers
Turncoat
We're left with 3 people. I don't want to jump into any conclusions. However, I agree it's possible that it was Turncoat and he tried to pin it on someone else.
What about the other suspects? Does Cain or Aubrieta take issue with Crow? Aubrieta is a little bit crazy; she could've done it.
Aubrieta I doubt it. Her and Crow focus mostly on guys, plus It's unlikely she'd have the mailing address. If she did, we probably would have all had the address.
Cain. I do believe is acquainted with crow in person. I don't see him as the type who would send toxic materials to some broad though. At best he either put her down nice and easy, or Cain secretly banged a ho.
Someone like TC has to really grind to install any value into the lives of others. Over the years and even through recent studies, I'd reckon TC is the type to secretly instill the problem and openly offer the solution. In turn he get's rewarded with appreciation, and he'll get to unwrap material goods, or monitor whatever people send her, for her safety.
Blaming SC would then be convenient. But then of course if TC doesn't unpackage her parcel deliveries, that would appear uncaring.