Many raging narcissistic extroverts claim to be introverts so they can try to deny the massive control freak that they are , and accuse others of being who they are. Treed carefully around that one.knife proof vest recommended

Introverts do avoid social situations but introverts can be talkative with people they trust & are comfortable with. And talkative also in a group if they have subject knowledge. I am not sure about the situation in this case. Only you can interpret that better

I can do something similar to this. I'm quiet most of the time, but I can talk someone's ear off if we end up on a topic that I know a lot about.

Perhaps she is more towards the center on the personality scale?

I can be, but only to one person at a time. If another shows up and there are three of us, I shut up. I never mastered "group speak"

'Have you ever considered having yourself checked out by a professional?' - her husband should have suggested that rather than dropping 'I think you have mental health issues ' on her.

She sounds like when she is with people she's comfortable with she does fine. Not necessarily narcissistic perhaps anxious?

Many people will describe themselves as introverted, yet on the surface don't actually appears to be. My personality at work is a contrast to my reclusive behavior everywhere else.

Who cares how she describes herself?

She just sounds like someone to avoid.

Distance yourself as much as possible (like always having " someplace else" you have to be) and stop giving her so much power in your head!

I sometimes engage in gab, but almost always with people I know very well.

Depends on how well she knows certain people.. How does she behave around strangers?