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.

I suspect for some of us , it may deal with comfort zone . Let's try this , I drive a car . Around home , I am comfortable driving without the use of maps or GPS . If I drive more than ten or fifteen miles away from where I live , I may not be as comfortable without the help of some kind of guidance system , or instructions , but I can still drive my car . On the other hand , there are some places where , even though I can drive a car , I would not be comfortable driving , perhaps up a steep mountain side on a narrow road or over a high bridge . Like wise , if the topic she is discussing is one she is very familiar with , or if the people she is talking to , know even less than she knows about it , she may feel confident to pass on what she thinks she knows , where as , if she is with a superior , who knows more than she does about a specific topic , she may be less comfortable talking to them . On the other hand , I've met some people who can't seem to shut their mouths , whether they know their topic or not . I've even met some who feel they have to get in the last word , even if the last word is nothing more than , " Yeah , but you know what I mean . " after someone else has spoken .

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?