Valerie was the first of the four polishes I chose that I painted on when I received them, and I was disappointed with what I found. She's still a beautiful color, but in my eyes she's almost identical to Jem, which I already own. I was glad that I at least didn't pay for the polish, but had I realized they were so similar I would have picked a different shade.
These photos might not be the best guides, but the only visible difference between Jem and Valerie is that Valerie has a blacker base, and even then it's hard to tell unless you really look up-close.
Bottom Line: Valerie and Jem aren't exact dupes (I don't think Zoya would ever do that to us), but they're so similar that I don't think there's any need to buy both of them. If you want a redder base, go with Jem; if you want a black base, go with Valerie. Either way, you're getting a beautiful purple polish with great shimmer!