Probably. It's really not all that hard to make a belt that looks like that with some Swarovskis or other good quality crystals from a craft store. Just look at all the fake Swarovski CC stud earrings and necklaces on ebay.
And I agree..if it WAS real, why would she only take $100 for it when she sold it for $600 on ebay before? Why not go back to ebay and get the same amount? I'm taking a wild guess that she was probably banned from selling on ebay and has to resort to craigslist now.