I'm not sure I understand the situation based off the linked post. I get the part that Meta won't let her create a duplicate, but what happened to her original account? Was her original account banned, or did she just lose her password or something?
To be fair, I was a Meta employee with inadvertent "duplicate" accounts, both I didn't use. One used an email domain I no longer had access to. The other worked for a bit but then instantly self-disabled when viewing 2FA options. It was eventually straightened out, but it took several tries to get it right.