Hi Wootcat,
The issue you have is related to the Skyrim Creation Kit not properly exporting facegen information to the .esp files. You will need to 'espify' the mod in Wyrebash, and then open the mod in the SCK.
Once you've done that, find the actor (for Lydia, filter the objects window with HousecarlWhiterun) and highlight the actor. After that, press CTRL + F4 and you will get a prompt to ask you if you want to export the facegen data. Obviously you'll want to click yes.
The facegen data export will create two sets of files in your Data directory, both in meshes and textures. If you look around in the files, you'll eventually come across a folder named the same name as the mod .esp - this is where the facegen data is exported to.
If you like, you can re-package these files in the mod and upload it as a 'fixed' version to whatever site you choose (so as long as their Terms of Service allows as such).
Hope this helps.
Edit: I forgot to mention, you'll need to de-espify the esp file once you're done, otherwise it will not load in the game.