I think the OP is saying that old stylist enticed existing customers to go to a new salon location by offering a coupon. Then, when the OP actually went to the new location, they did not give her the benefit of the coupon, but simply charged her 10$ which is the price at the "new" salon for a child's haircut, saying that she was a "new customer." The dishonesty is that she led the OP to believe she would be an old customer at the new salon because she was an old customer of that stylist but she was not charged as such, and did not get the benefit of the coupon.
I also think the coupon probably said get 5 haircuts at the promotional price, in an attempt to keep the customers who moved with the salon to the new location loyal (like a punch card, after 5 punches she would have used it up).
Maybe at the old salon, the discount would have been more meaningful to the OP but still would have allowed the salon to get a "living wage" off the cut (I know I pay 18$ plus tax for my DS3's haircuts, and over 20$ for DS12), but at the new salon the kids' cuts are so cheap anyway, they just charged her the normal rate, because ending up with a 2$ charge for the work of doing a haircut is not something the salon wanted to do. The actual individual stytlist who actually gave the OP the coupon may not have had anything to do with the salon ultimately not honoring the coupon - she may have given it to OP in good faith, and then found out that the new salon would not honor it.
It's all just guessing, but that's what I'm getting from it.
Jane