I would start by contacting a psychiatric organization like MAPS, or personally reaching to it's board members or practices that are listed there. I don't know of any legal organization that will put you on ketamine therapy without having you as a patient from beforehand or having your psychiatrists recommend you to them for treatment.
Is she seeing a psychiatrist? Antidepressants stop working all the time, she should be having this conversations with her psych or telling her psych that she's stopping treatment and finding someone else because it's not working. If she's on any other basic meds like sleeping pills or anxiety meds she should be able to get a prescription for them from a GP or any cheap synch in-network only by saying she's already taking them.