You are not a special snowflake for going after a refund. You had had a negative experience with 2 locations of this chain, addressed the problem both times without satisfaction from management, and so you knew you would never use this certificate. I just heard from a small business owner that each new customer is worth $10,000 to the life of a business, so they lost a lot by chasing away a regular customer. You disliked them so much you wouldn't even return once more! I'm glad that you (politely, I'm sure) pushed to get your money back.
But, they didn't chase away a regular customer. The OP is firm in that she will never go back there, no matter what.
It's unfortunate that her husband didn't remember her negative experience at this place - but that's not the salon's fault.
They did chase away a regular customer! Just because it was four years ago doesn't mean that they didn't screw up and lose a customer.
And it doesn't have to be anyone's "fault." The underlying principle is that the person who has the gift certificate should be able to use it. This business has made that impossible by not providing good service.
And the idea that she should regift it seems rude--would you give a crappy gift to someone?
If the reason she couldn't use it was because of something specific to her, then that might be OK, but the reason she can't use it is the business' fault. They bear responsibility for not being a good business.
And its true that just because a customer gets their money back doesn't mean they're right. But, at the same time, businesses can refuse to serve people if those people are impossible to please.
That doesn't seem to be the case here, though.
I don't think there's anything Special Snowflaky about getting your money's worth. The sheep analogy is pretty close.