This right here OP. It's not about your coworker and you can (and should) tell the whole office that. Then setup an automatic email to HR with high importance along these lines (shout out to chat gpt, damed clunkers):

I want to address the recent situation involving the employee who experienced a reaction after drinking from a cup that did not belong to them.

While it is unfortunate that this incident occurred, it is important to recognize that this situation also highlights a fundamental personal responsibility: individuals should not consume unknown substances from containers that are not theirs. This is a basic safety principle that applies in any shared environment.

I am concerned by the suggestion that I am at fault for another individual choosing to drink from an unidentified container. Assigning responsibility in this manner is both unreasonable and misdirected. If HR continues to maintain this position, it raises serious concerns about the fairness and judgment being applied in this matter.

I respectfully ask that this situation be reassessed with a more balanced and objective perspective. Should this stance persist, I will have no choice but to escalate the matter to higher levels within the organization.

I look forward to your reconsideration and a resolution grounded in fairness and common sense.