Hello @Shaz51
As you are probably aware, my Mum was with me for her last ten years, of which the last three were in Residential Care, about 750 metres from home - so "another room in the house". (Hope people don't get sick of reading the same story).
Mum and I had a really good run for both of us, but physical limitations and liabilities in terms of the potential for accidents were becoming a higher potential issue and risk. At one stage, Mum actually fractured her upper leg bone by twisting to turn off a lamp.
For most of the time, Mum was lucid and even remembered visiting children's names till quite near her time of passing. There were a few 'aberrations', in terms of thinking and perception, that seemed to be quite spaced out in terms of occurrence and really did not seem to be connected with each other, as might be expected in a gradual decline of mental faculty.
Those occurrences seemed to me to have been more a selective venturing of the mind to another place, almost as a reverie, rather than an unconscious slippage of faculty.
As a consequence of my own experience and, while I am aware that I know virtually nothing of the circumstances existing for you, I would not be too concerned about occasional distractions.
However, I can certainly understand your distress at seeing someone so close experiencing what must have presented as a distressing event. I very much hope that the experience will not be repeated. Hopefully, it was just a matter of co-incidental factors coming together that caused an unpleasant sensation. We all have those at some time or another. For older people such events may seem to be somewhat more threatening.
With my hope that the experience will not re-occur. Also, it is worth remaining aware that the least amount of distress and anxiety we show or express, the less will flow over to and reinforce unpleasant sensations or reactions for your Mum.
With My Very Best Wishes
@HenryX