What OTC drug would [a] cause bloody vomiting [b] be small enough to hide [c] be easily obtained in either a convenience store or grocery store?
search terms: Most of the search terms came up with signs and treatments of suspected OTC overdoses; drug overdose OTC, drug overdose violent reaction, OTC overdose vomiting, suicide overdose, OTC suicide
PS - you guys were a big help with my last question! Although I'm not finished with that screenplay, your help got me over a big bout of writer's block.
[EDIT: To clarify on small enough to hide, I meant that she was able to hide it both on her person (to get it home) and in her room (not so much of a problem in the story), most likely in a drawer.]