When Twilight goes to far with a prank that ends the life of one of her closest friends, how will she cope with a loss of her own doing?

Inspired by the effects of a Visine overdose as a party prank. I'd rather not talk about why I know that, but do try not to attempt it, okay? While most people will survive these days if the dose isn't too much, it is highly toxic in anymore than minute quantities, and can easily kill from a single vial of it.