Cosades wants me to talk to Sharn Gra-Muzgob about the Nevararine. Unfortunately when I go talk to her she does not offer me this option for dialogue. Nothing I ask her from her list of dialogue choices will prompt her to give me the quest. What can I do? Thanks!

Just to be sure....
Has she asked you to go find the skull of Llevule Andrano from Andrano Ancestral Tomb?
You have to do that errand for her before she will tell you about the Nerevarine.

If that is the part you cannot get, you can start her little quest with Journal, "A1_4_MuzgobInformant" 10

Are you using any mods?

Are the topics "Errand" or "Nerevarine cult" available? Those are the topics which move her quest forward. Also, make sure you got all the necessary information from Cosades before you went to talk to her.