I realized that, though I've told the story, Nisha's in-game profile differs a bit from the overall tale.  I present to you Nisha's profile which is visible in-game if you use the add-on Total Replay 3, downloadable through the Twitch app:

Still reeling from the pain of losing her mother, a few years had gone by, but as of her mother's passing, both her parents were now gone. It was a struggle to keep up hope and it took everything she had to keep going. She quested through Westfall with the ominous green presence of Argus looming in the sky. It was a trying ordeal and by the time she witnessed the Rise of the Defias, she was asking herself if being a hero was truly worth it.

She was sent back to Stormwind to tell the King what had transpired at Sentinel Hill and when she got to the Keep, King Anduin Wrynn's words to her changed her entire perspective. He said to her, "Stormwind honors your service to the Alliance". Suddenly, everything she had gone through, every challenge she had faced, was worth it; she was in the service of the Alliance!

King Anduin has since become like a best friend to her, learning about the loss of his mother, whom he never really knew, and now, with the loss of his father, King Varian; their stories were suddenly so similar; now both of his parents were gone too. She was all to familiar with the pain he was going through and Anduin's loss helped her work through her own.

She is the first of a new mage spec, a Light Mage, and became Soulbound to King Anduin by inadverdantly triggering an ancient magic in music after singing his theme, 'A World Divided', to him.