Hi Shandy
It sounds like your Mum is now at the same stage my dad has been for about 4 years. He has had a succession of pressure sores (grade 1 or 2) through all this time. He is in a hospital profile bed with an airflow mattress too and has spent the majority of his time in bed in his room as sitting in a recliner chair for longer than half an hour at a time tends to cause more pressure sores. Once his skin is stable again, they start getting him up occasionally but I have to say it's a bit of a vicious circle. The problem is caused by the fact he is completely immobile and very underweight at only 6 stone.
As he is uncommuncative and unaware of anyone/thing around him, I take comfort that he no longer seems to need any stimulation so the long periods alone in his room don't worry him. Of course I have no way of knowing if this is the case but there's nothing I can do - all my spare time is spent with him and the NH is understaffed so the care workers and activity co-ordintors spend most of their time dealing with the more challenging residents.
So based on my own experiences over this long time (as I don't have any medical knowledge) , I would say that, yes, it is likely your Mum will be able to get up again once the sore is healed. As far as whether this is the end for her, I wish I could answer that, but as you can see with my dad he has lived with pressure sores and being bed-bound for a very long time and although he has many other problems associated with being at the severe/end stage of the illness, he is showing no signs of going anywhere. This is both a blessing and a curse.
You may have done this already but I would ask if your mum could have a visit from the skin integrity nurse and if you could be there to discuss things with her. They will give advice about wound care but also what is appropriate in terms of sitting out etc. Also, I would check what the NH is doing about making sure she is kept stimulated/entertained whilst she is in bed
What I would say is that this is a very difficult situation to deal with - being in a 'limbo' state and with no idea how long all this will las, so you have my sympathy
Hope this helps
Take care
x.