Hi Sabato
May be bad, may be good, may be the only practical thing!
What you need to do is
1. to understand the extent to which your Mum is disabled by dementia. If you lived with her until she went to the home, then you will understand already.
2. to understand whether Mum has become worse since entering the care home - this often happens as a change of environment can cause problems.
3. to understand what is the alternative to the wheelchair. If it is an armchair, then is she safe in it? If staff need to move residents around a lot, then a wheelchair may be a practical option - though not best for her of course. Other times she may be in a normal chair.
4. to understand how her day is organised. Perhaps she is in a chair because you come the same time to see her each day, and that is a mealtime, and that is the best way to move her to the table.
You really need to find out exactly what happens to her from the time she gets up in the morning, to the time she goes to bed at night. If nothing else, spend a day with her, if you can manage to take the time. That will also enable you to understand the practical issues of her care.
Of course it may be that she is simply left in the chair, staring at a wall, which is really bad.
So, take time to find out. Talk to the care assistants and management.
Good luck