Her NPI won't change, but her tax ID must be linked to it. She needs to go in and update her NPI with her new tax ID.
Changing her tax ID is a big deal. Like Linda said, all the insurance carriers need to be notified. Medicare requires CMS forms to change the tax ID. Our local BC requires new contracts to be signed. Etc. etc.
You need to ask her why she changed her tax ID#. Then tell her that all insurance carriers need to be notified and that can take time, and it can affect payment.
Michele