I think you have to treat difficult people like horses - send clear messages.
In the past you have said (I think) that you have to go along with her because of your OH.
Now it could be she is anxious in hospital. So you could say you and OH work office hours. Please will she list the things she needs and let you know each day at 5.30 p.m. and then you will do your best.
If, after this warning, a text arrives in office hours text back - "Interim reply as currently working in office".
Manage her like a horse and give clear signals of boundaries.