And now she turns up her nose at jazz and all its manifestations-likewise almost everything else distinctly racial. In this context, what is the meaning of "manifestations"?

In this context, "manifestations" is meant as display of proof, demonstration and indication of jazz. "Manifestations" is used here to tag anything--an event, action or object that shows or embodies the music. It also includes any form of expression of jazz.

As stated in Wikipedia manifestation is " an event, action, or object that clearly shows or embodies something, especially a theory or an abstract idea."

This means that the word manifestation defines the effects of the music on her