So she gets Covid-19 and has to be admitted to hospital with complications due to her health issues. She’s now taking up a much needed bed. She passes it onto the nurse who tends to her. The nurse becomes infected, develops breathing problems, ends up on a ventilator and sadly dies. She was young with 2 children.
You know what, at some point this has to stop. It's outrageous. I would have argued that such a thing was theoretically possible at the beginning of this crisis. Not so much now.
There are ICU beds sitting empty everywhere. There is lots of capacity for the people who will need them over the coming months.
Someone this vulnerable wouldn't be put on a ventilator anyway. No doctor would consider that proportionate or kind treatment. Ventilators do damage and you need to have a good chance of surviving them to be considered.
Garden centres are often mostly outdoors - there is a tiny chance of this person picking anything up in one. You can safely keep your distance so the virus won't spread there.
In most parts of the country, 1% of people have the virus atm. You can see the data on the ZOE Covid website. Therefore going to any garden centre is low risk. It might have potentially given that person huge pleasure to get out though. That counts for something. We aren't built to be shut in, away from people.
Most nurses are at very low risk of dying if they get the virus. Only a few unlucky ones have passed away which is very tragic, but it really is a minority.
If you have had years of chronic health issues or you know your death is somewhat imminent, it is your personal decision about what you do. Ideally you will stay 2m away from people at the moment, wash your hands, etc. Be socially responsible. But these people matter too and a great many would rather risk the virus and live a little instead of sitting in, seeing few people and having no fun. Other vulnerable people who want to shield should be supported to do so.
If this virus ends up being here to stay (and it likely is given that even if we get a vaccine, it is highly likely it won't be effective in everyone because many aren't) then people like the OP describes need to be free to make these kind of decisions for themselves. It is not for other people to tut and disapprove. There are plenty of epidemiologists who are saying this virus is going to get everywhere and there is really no stopping it so judging people who want to get out is really very unkind. You have no idea what they have endured for the past few months.