Take some photos on your phone, show your local chemist- see if he can supply laxatives or an emetic that look the same.
swap pills and let nature take its course.

But like "OK" said, advising her friends parents sounds like a good move too!
I too, am pretty sure 3 pills classes her as a dealer- and is an open invite for the police to trash your home.
Something to also check- I think as far as the law is concerned- as a dealers residence- you could (in theory) forfeit the house. This particular law is aimed at big time dealers- not dumb kids with a couple of pills- but drug dealing is going to look bad on a resume or stop a police clearance for a decent job or career.
If you happen to be a licensed firearm owner- and drugs are found inside your property- its almost guaranteed that you will face an expensive fight to get your firearms back.
In my opinion, the drawer you searched is in your property and you are responsible for what goes on in the property.
Any betrayal of trust was by your daughter when she brought illegal substances onto your property.
You would not have searched for the drugs without good reason, after all its your daughters welfare and health you are looking out for.
stephen