You should probably say, "Welcome back." She is a gem of a salesperson, and now she is even more so. People do all sorts of things to alter their appearance, whether it's dying their hair, getting colored contact lenses, or having their teeth whitened, and that's strictly their business.
She is still the same excellent salesperson, complete with the same skills, energy, tenacity, and presumably high level of customer service. Besides, if any of her customers happen to have similarly adorned airways, they are going to sense a stronger bond with her, and that can actually lead to increased sales. And further, even if your customers are a staid and serious lot, their first priority in dealing with this salesperson is her competence and support, along with the quality of the product.
If her sales do start to tumble, she will be the first person to try to figure out why. And, if she determines that the culprit is the carat, she will pop it into her jewelry box in a flash. At this point, you have a confident, independent, and successful employee who literally shines in her work. There's nothing here that should get your nose out of joint.
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