Honestly, i would NEVER EVER buy a Chanel fragrance on EBAY. I know you want a vintage but, a lot of them smell horrible bc they have not been stored properly. I would, without a doubt, just go to Chanel.com and buy it from them. I have bought a lot of fragrances from Chanel.com and their fragrances are always wonderfully fresh stock and their customer service is the best i have ever experienced anywhere. Plus, they can gift wrap it for you too and it will look beautiful, she will love it.
eBay also has many fakes too. I think most of the experienced BN'ers would agree, by experienced i mean those who purchase, trade, or sell a lot.