Wintergreen is an EO to use with caution because it contains methyl salicylate which thins the blood. People have gotten into trouble and even died by over-using liniments that contain methyl salicylate or by using these liniments while taking blood thinning medications.
Yes, wintergreen can be safely used as a flavoring in food, because it is used only in tiny amounts. Yes, it can be used in essential oil blends for skin use, but is recommended only for spot treatment for short periods of time for people not taking blood thinners.
I would personally avoid using wintergreen in my products, since I don't want to get tangled up with the liability risk, since I know wintergreen has issues. (And also because I don't care for the memory of "liniment smell" that wintergreen triggers for me.)
But I do see the lady's argument -- if only a very small amount is being used in the product, it is reasonably safe.
What about spearmint instead? It has a mild, sweet minty fragrance that many enjoy and no methyl salicylate issue to worry about.