This is definitely a book by David Zindell, most likely Neverness. The woman who becomes a godlike cybernetic entity is called the "Solid State Entity," and she's one of several such AI deities in the book, and in that larger fictional continuity, which is also the setting for his trilogy, A Requiem For Homo Sapiens.
One of the most distinctive aspects of the book is the existence of a guild of hyperspace pilots who navigate through the universe by discovering new and unique mathematical theorems.
Neverness is one of my favorite books, but I never read the trilogy, so the only reason I hesitate at all about the identification is because I don't remember the supernova viewing party. The mathematical pilots and the Solid State Entity are both in Neverness, but they are likely to also appear in the trilogy as well.