Do not utter the term,

 

without the credential, naming a medical diagnosis doesn't help you. Think of her as having "narcissistic personality traits", or simply a narcissist, and keep it to yourself.

You cannot control her.  What you can control is you yourself. Do not react to what makes you uncomfortable, like her tone or mannerism (they are there to agitate, seeing you squirm brings her pleasure). Make her antics have no effect on you.

Smile. Focus on the issue.

You cannot change her. As you have said, to extricate yourself is the only way.

HR always makes the management look good.