How sick can you get ODing on a laxative? If you were to do her permanent damage you're setting yourself up for a lawsuit.
I don't think "getting in trouble with the boss" would dissuade her in that scenario.
fok it, drop a four bar xanax in her soda pop...lol that will put her asleep. Then she will get fired and she needs to hit bottom before she can get better. You would be starting an "intervention" of sorts