I've seen two similar things happen.
Here, in many New Age stores, the employees are 'trained' for common things. They know that this candle is for love, this incense for good energies, and this bell is to call the wind elementals. They don't practice it, they read it on the little paper that came with the product. OR, more likely, they have been taught by the store owner, who usually KNOWS more about 'occult' things.
So, if the shop is small and doesn't have many employees, some times you can talk to the owner and discuss such things, if they are open-minded. And i hope the girl you are talking about is - specially if she got so excited, probably she wouldn't mind learning from someone who has many yaers of Tarot study and practice, such as you.
However, some shop owners (and that happened to me)...they like to say they are mages or witches. They read tarot, and they bless the incenses of their shop themselves. And it's is great. But they usually don't want you to discuss what they have said. They get offended, because (specially if they have many clients) they 'know' - and who are you to suggest they might be wrong???
I once tried to discuss something with a shop owner and ended up with all her employees and the clients looking at me as if i was a ignorant trying to show off. Hey, i'm sorry, but when she came to talk to me about tarot, assuming i knew nothing about it, and i didn't agree with something, i let her know that this wasn't MY vision. But if it's her vision, okay, i'll respect it, and if it's something useful, i'll add to my mental tarot journal.
Of course, i really think you should try to teach this person more about tarot, since she sells it. Tell her that you collect decks, and have read for many years, the way you described sounds like she'd be excited more than offended. But beware the know-it-alls of the New Age stores, they can give you quite a headache
Miss Y.