Could it be that they are pulling your mother up out of chairs by the wrists? My sister witnessed staff doing this to our mum: not out of malice but simply out of ignorance about how to move her properly.
Mum was admitted to hospital soon afterwards and I found bruises like those you've described. Even my sister thought I was paranoid, but a nurse on the ward confirmed that the bruises should not have been there.
I understand your reluctance to speak up--dealing with this kind of thing is a nightmare--but I do think you need to raise it.
Best wishes to you and your mum xx
