I don't think I would. I would maybe ask her for more photos, or take a photo with a piece of paper with her ID written on it next to the bag (it would make me feel better for such a large purchase.) Also ask if she is selling anywhere else/has an ebay id you can see feedback, definitely use a credit card just in case you need to file a chareback..
I was just thinking about this - if you are definitely interested in this bag and intend to buy it, why not ask her if she would be prepared to list it on eBay?
She may not have done that to start with, as she didn't want to waste money on listing fees, with no guarantee it would sell, but if she knows she has a definite buyer, that might be a different matter.