While it could look like grab bruising, it could be , as was the case with my Mum, that her medication was causing her to bruise/bleed very easily and the slightest knock, rub or, yes firm grip to help her rise, would bring some spectacular bruising.
None the less I too would want it discussed and I guess that, the day after a BH weekend there will be a fair bit of catching up to do, so waiting until 3 pm is a good idea. Then all you can do is keep a close watch, and let them know that you are supervising Mum's bruises. Sorry I can't help more.