Just as SS don't have the capacity to visit every family where mums (or dads) shout loudly and throw things down when they are highly stressed or not coping, they don't have the capacity to deal with carer stress, MH issues, loneliness and suicidal thoughts that happen to many when caring for many for prolonged periods.
It's not just families that crack, my relative had two carers at different times that reached the end of their tether, one stormed out and one started crying after spending two hours clearing up bedsheets and the person covered in shit and they then had an accident immediately afterwards, and moved about covering everything all over again. Should they have cried? No, they were professional but in that moment, the demands of the job were overwhelming. My relative was very difficult and out of control a lot of the time, that's stressful. Doubly so when it's your relative that's dying.
How much harder to be the carer of your family who might be just as difficult as when you were younger, but now they are very old, can't hear what you say, may have cognitive decline/dementia, may ask the same thing 1000 times, may disagree with everything you do and so on.
No-one turns into a saint in these situations, not the carer and not the person being cared for (I've been both).
That's not to say genuinely concerning situations shouldn't be reported, but to me, raised voices, throwing down some things and storming out isn't that. I've done that with my teens for starters when their behaviour was unbearable.
Things I'd be concerned about would be cruelty, mishandling (like being too rough), over medication to get people to sleep/sedate them, ignoring basic needs, and any type of bullying (sounds like the OP's mum was shouting at her, this again is normal in older adults, indeed all adults, lots of people shout!) Beyond that, clearly physical harm, putting people at risk of falling.
SS are highly motivated to continue family care, it's much cheaper than going into a home for them, and some homes also suffer from the above problems, especially over-medication as it's very difficult to manage lots of very old people with few staff and that's one way to do it.
Even if the OP never comes back, it's interesting to think about this, and to decide what you would and wouldn't do (I'd be very concerned for my friend and try to get more support for them).