In a nutshell, no. The temptation to do so will be overwhelming, but here’s a short list of reasons why you should not:
- The narcissist will have warned the new target that you may confront them & they will be defensive.
- You will appear “crazy” or “deranged” just as they were told you are.
- You will seem jealous & bitter, simply trying to destroy their “good thing.”
- You will make the narcissist seem more desirable, as you fight for him.
- Your warning will likely strengthen their bond as the target pushes back against how she FEELS about the narcissist. She has already been seduced by his charm & warned that you’re a lunatic. Your claims will seem to give his credibility to his warnings about your instability & bitterness. This is, after all, her soulmate you’re talking about.
If you choose to warn the new target in spite of this, I would recommend that you go through a mutual friend, if possible. The new target will not be prepared to hear from a third party about the malevolent acts of her soulmate & one true love. You have likely been vilified for months to the narcissist’s fan club, including the new target. They will pity him for the abuse he’s suffered at your hands.
The only upside of warning the new target is the possibility that red flags will be recognized earlier, but there is no guarantee. Going forward, remember that the new partner is a victim, just as you were. There is no reason to disparage them or make their life more difficult. Sadly, it’s simply a matter of time before the narcissist destroys them.