Sunbringer is not The Sunbringer

The Sunbringer

New Sunbringer

As you can see, one has massive... one has star shaped pupils, while the other doesn't. I have a theory that, since The Sunbringer's technology is so advanced, The Sunbringer created Sunbringer as a replacement and put her soul(literal soul) into the new Sunbringer. That's why she can live for hundreds of years, similar to Raiden Shogun and Ei, or she's just a dragon thiren and can live for a long time.