I have that problem to.. ;;
First, look for a logo ! Normally replicas have logos, usually on the front of the dress !
Also, sometimes if the item is too cute to be true, it’s a replica aha ;;
If the store doesn’t have a watermark on the pictures, reverse google image search it ! Sometimes you’ll get the original taobao listing and if it has a name like (translated) “JAPAN AMAVEL AMO ZIPPER CUTE SUMMER 2014 DRESS” and it lists a bunch of brands, it’s most likely a replica aha ;;
If you’re really unsure, I can help ! I’m pretty good at spotting replicas ♥
It really sucks but you have to be careful ><
I hope this helps !