"Why do you ask for the PSU"
It might still be a poorly functioning PSU.
"High watt recommendations are just for cheap PSUs"
Perhaps, but the closer to maximum you stress your PSU, the hotter the capacitors are and the shorter their life. I tend to get overly powerful PSUs and only use models tested by some independent site so I know they are good ones with low ripple, stable power delivery aso. BeQuiets are ok, but do not usually really excel in tests.
"Will the chipset driver from AMD replace the Asus chipset driver?"
It should. Basically driver from Asus is likely just an older AMD driver that might have some Asus branding and maybe they added something or removed something. Usually they are just older and thus recommended to use the ones straight from chipsets designer/maker (AMD in this case)
"DDU seems a bit overkill, as the prior gpu was also AMD"
Not necessarily as drivers do detect which GPU is installed and different models could perhaps have for instance different registry keys due to different feature sets and whatnot.
"Powersaving is not very likely, as it always happens while she is doing something, like browsing, writing, fotos etc."
What I was after was, if computer notices it is not used heavily, it might kick in some power saving features and/or lower voltage to some parts and cause the issue, especially if PSU doesn't work well with power saving features. It is a bit difficult to explain what I mean with limited English skills.
