She was a genius of sadness, immersing herself in it, separating its numerous strands, appreciating its subtle nuances. She was a prism through which sadness could be divided into its infinite spectrum.

This quote is saying that the person was very skilled at understanding and interpreting sadness. She was able to look at sadness from many angles and could figure out the different shades, complexities, and nuances within it. She had a special ability to break sadness down into its individual components, which could make the sadness even more powerful and beautiful. The quote is saying that she was like a prism that allowed the sadness to be divided and seen in all of its infinite colors.