he
Was
a drug that she thought of.
he
Was
a drug that she convinced herself to take
knowing it would harm her.
he
Was
a drug she was addicted to.
so when he left, he left her thirsty.
he
Was
a drug.
Yet She
Was
his poison.

and poison is something you take knowing it kills you.
but you want it, and you're not sure why.