Supernana this was obviously a very traumatic event to witness - I'm glad your neighbour had a peaceful death in the end.
As a nurse who regularly does end of life care in patient's homes:
I don't know the rules or guidelines but doctors don't prescribe a package of drugs for every patient 'just in case'. I don't know the official statistics, but not everyone by any means needs the syringe-driver. I've seen a number of cases where the drugs were not needed and are sent to the pharmacy for disposal after the patient dies. No idea of the cost but there is usually, morphine or similiar, plus meds for secretions, nausea, and agitation/hallucinations mixed in the syringe-driver and top-ups of each drug can be given by a nurse when needed.
Even if the drug for secretions, Hyoscine, was on hand I don't know if that would have been any use for a pleural effusion. Maybe the lady needed to have the syringe-driver set up and administered to prevent the build-up of secretions in the days beforehand, but that's a different matter.
I don't think the GP was negligent - she made a clinical judgement, and at the time of the visit the patient was calm and peaceful.