Welcome to healthcare magic
From your description it looks like your mother could be having scalp psoriasis
. In psoriasis it will be a scaly plaque , not a scab, but both can look almost the same.Without an opportunity to closely examine the lesion, I would not be able to accurately specify the condition. You might need to consider a consultation with dermatologist
For scalp psoriasis you may apply warm oil (not hot) over the plaque and soften the scales and try to remove it. You may use a shampoo containing coal tar
and salicylic acid
for washing scalp. For scalp psoriasis with thick plaques you need a stronger steroid lotion like clobetasol propionate
than synalar preferably a combination with salicylic acid 3 %. You need prescription from your doctor for this.
Hope this helped