I'm far from young & I have people ask me from time to time if some of my jewelry is real. I usually just say "Well, what do you think?" I could care less what other people's opinions are of my jewelry or me in general. Life's too short to worry about petty crap. I have designer bags & unbranded bags; my jewelry is generally unbranded because I buy what I like. I have all kinds of pearls, gemstones, & diamonds. I don't live an extravagant lifestyle but I do tend to spend my money on quality. I was wearing some of my South Sea pearls one evening to dinner & had a woman comment to me about how pretty my costume pearls were. I asked her what made her think they were costume & she said real pearls aren't that large. (Mine are 11-12 mm, not gargantuan) I told her they were White South Sea Pearls & she said she had never heard of such. My response at that point was to tell her Google was her friend & she should Google South Sea Pearls from Australia. She was somewhat taken aback. I will say that her companion looked a little embarrassed by her comments about my jewelry.
People will be tacky & make comments about things that are really none of their business. Normally, I just ignore them. I would never question someone about the genuineness or authenticity of the jewelry they wear. What one person chooses to wear is different from someone else. If it makes you smile & you enjoy wearing something, why not just enjoy it! I will comment sometimes on someone else's jewelry but it's just to say that it's pretty or looks good on them.
I would have been embarrassed if I was her companion too, I mean she could have just said "nice necklace" and that would have been it, your pearly sounds gorgy though.