I no longer go to a hair salon since my stylist for the past three years does hair in her home and charges a flat $65 for cut, color, and blow dry. However, when I did go to a salon, I usually tipped the shampoo person $1--$2-$3 for the holiday (the stylists in our local salons take care of the shampoo person, and the $5 that your mother is tipping is more than generous). I usually doubled the tip for my stylist, who I had for many years (I dropped her when she always found a reason to up the price--I had retired--and wanted me to be blonde--"you will grow to love it.")
So, for your mom, I would, at this point, give the shampoo person(s) $5 (cut it back after the new year) and, if money is tight, maybe $20-$30 for the stylist. If she has been going there a long time, the stylist depends on the reliability of your mother's business and probably is not worried about the size of the tip.
The next time that I hear salt and ice together, it better be in a margarita!