Does Caroldiva authenticate anything other than Vuitton? I looked at her website and it seems like she only works on LV items.
Since most stores won't authenticate bags or give written statements since they can be copied and sent along with fake bags, they are leading authentication sites which, for a small fee, will authenticate your bag and issue a statement determining your item's authenticity which cannot be copied:
www.mypoupette.com
www.caroldiva.com