For what it's worth and if you're still reading replies.
I 'm glad to hear your nephew's JW is waking up to her religion that is always a good thing. If she converts to Judaism now that's her business. Her words to her family about the expected shunning are brave even if wishful thinking because as a witness she would know exactly what the consequences of her actions will be from her friends and family, if, her family are active JWs that is. She will need support when that shit hits the fan.
Oh and btw if it works out your nephew dodged a JW bullet for sure.