When the PCS is still this 'young' it's pretty likely that such over-stimulating environments will exaccerbate your mum's symptoms.

As time goes on, it may happen less freqently but quite dramatically even after perios of noticeable improvement. It's worth encouraging your mum to try to notice the warning signs that that's a bad day to be in a noisy, brightly lit place. Hopefully then she'll be able to juggle her days when a dizzy/foggy/fatigue hit is likelly to occur.

Good for you for looking into this for her. PCS can be lonely if noone around you really gets it.