I would tell her. I'd tell her in the gentlest of ways but, nonetheless, I would say something. I think that if you present it to her in the right way, she will appreciate it. Something like, "You are my friend and because you are my friend there is something that I want to tell you. I am not judging you and I don't want to hurt your feelings, but..." How could she be mad at you for that?
I would want to know. I bought a fake bag on eBay by accident once and didn't know it was fake for a long time. I saw someone carrying a real one and I immediately knew that mine wasn't real because the difference in quality was very apparent. I was so embarassed when I realized that I had been carrying a fake. Some people don't care about carrying fake bags - those are the people who want to look like they are carrying real. We all talk about some certain bags screaming "Look at my Coach (or fill in the blank) bag, everyone!" and we are talking about the real bags!! Typically, people who knowingly carry fake bags want that kind of attention. I didn't want anyone to think that I was one of those types. I am guessing that your friend isn't either.
I would want to know. I bought a fake bag on eBay by accident once and didn't know it was fake for a long time. I saw someone carrying a real one and I immediately knew that mine wasn't real because the difference in quality was very apparent. I was so embarassed when I realized that I had been carrying a fake. Some people don't care about carrying fake bags - those are the people who want to look like they are carrying real. We all talk about some certain bags screaming "Look at my Coach (or fill in the blank) bag, everyone!" and we are talking about the real bags!! Typically, people who knowingly carry fake bags want that kind of attention. I didn't want anyone to think that I was one of those types. I am guessing that your friend isn't either.