I’ve been pondering your question all day. The answer might sound strange, but I’ll see if I can articulate it. Since you ask…
Frustratingly I can’t easily track down the year of the show. I know it was around Christmas (probably early December), but I’m not sure of the precise year — probably around 2008–2010 is my best guess.
When I saw her she mentioned having recently worked with a vocal coach, a lot of the issues with her mom from the 90s (and earlier) were being dealt with, and she had been performing solo for quite awhile. I believe those factors contributed to a special time in her career: she seemed more self-confident, self-reliant, and at peace than I can recall her being in her younger years.
Additionally, she possessed a humility that you don’t always see with established performers. It’s one of my favorite traits in acts/bands/singers who have experienced great fame and longevity: to see that humility, that knowledge that the stars aligned with their talent to create success. Not everyone has that humility and gratitude. You can’t fake that. When an artist/singer has it, it enhances the performance because there is a different experience and connection with the audience, the fans.
The final layer may sound hokey (and you can dismiss it entirely without insulting me), but you have asked for my take and it would be incomplete if I didn’t mention it. Her faith. She is one of those talents that looks beyond herself in everything she does and always gives God the credit. Her knowledge in that relationship is a foundation in everything she does. I think that confidence in His gift (ie, her voice/musical talents) combined with the years in front of audiences, the years of honing her craft (including performing solo for many years by the time I saw her), the extra vocal training, and a setlist that included beloved Christmas tunes contributed to a beautiful, intimate show.
The Paramount is a gorgeous theater, too, so that doesn’t hurt either!
(That was probably WAY more than you were expecting when you asked your question!)