Unofficial Oblivion Patch

This mod on Nexus Mods may be of interest to include in the Unofficial Shivering Isles Patch: Nanette Don fix by gekkedaan.

From the mod page's description:

This mod makes Nanette Don talk to you again when you've chosen to kill the Gatekeeping using Relmyna's Tears, after finishing the main quest in the Shivering Isles DLC.

During the quest Through the Fringe of Madness, when you've chosen to follow up on Nanette Don's information concerning the Gatekeeper being vulnerable to Relmyna's tears, she will refuse to talk to you ever again for the remainder of the game. This mod makes it so that when you become the Madgod she will resume normal dialogue again, regardless of the choice you made.

The UESP notes that one of the rewards for completing the main SI questline is that "citizens of the realm will address you as "Lord Sheogorath" or "Madgod", and mention how honored they are to be speaking to you or ask for your blessing". It might therefore be appropriate for Nanette Don to greet the player in such manner, instead of the hostility she previously showed the player character (before they became Sheogorath).