I would take every possible action not to take their medication, whatever they may think. My actions are determined by my thoughts not their.
At the same time I don’t think it is so terrible that a lot of people don’t understand your talk about imaginary friends. Very few people can talk to everyone about everything. Depending on the situation and the person you talk with, you have to look for a suitable subject for conversation. Also when you can talk about something, you have to formulate what you want to say very carefully to make yourself understood.
If you consider it very important to talk about hearing voices, you can maybe find some other people to talk with in forums for voice-hearers in general (not only psychiatric patients) like Hearing Voices Network - Index page