Friend slipped me a pill. What do you think of this situation?

OK, we just finished the clroom portion of medical school yesterday and start rotations in a couple weeks. We all started celebrating at like 10 am and only got like 2 hrs sleep the night before. Anyway, later on (like 10 pm) we're at the bar and my two friends (female clmates that I have been quite close with) decide that they want to take an Excedrin for the caffeine. I told them that was a bad idea because acetaminophen is rough on the liver especially when drinking. Plus it's a pretty stupid way to get your caffeine fix, (yes, these are med students!). They wanted me to take one and I told them no and repeated my reason for not wanting it. Apparently they thought I wasn't quite peppy enough so they decided to do something about it. About an hour later I saw some pill fragments in the bottom of my drink! I instantly became enraged and slammed the gl down upside down on the table and yelled "why the eff is there a effin pill in the bottom of my drink?!?!" I told my "friends" that we were done and walked home a couple blocks. Anyway, this "friend" came after me and I told her that we are NOT friends anymore and please eff off forever! She kept calling and hollering outside my door at like 1 in the morning. I finally threatened to call the police and reminded her that her career would be ruined if she didn't stop. She finally left, but keeps wanting to get together to talk about it but I don't think there's anything so say. The thing is that I never even heard the words "I'm sorry", just a bunch of crap about how I did her wrong by not talking to her and leaving her by herself or some crap. (BTW, we're in one of the safest cities in the midwest, no danger!) I think she's insane and don't want to be friends with either of them anymore, but they swear I'm overreacting. What do you think? I think it was an unforgivable act and also incredibly stupid for med students to be slipping people pills. I don't feel like I know them anymore since this was such a colossal failure in judgment and demonstrates a level of idiocy I never thought I would see from these people. Opinions?