October 2019 - last edited October 2019
@lince918 The first thing to do is delete the five cache files in your Sims 3 game folder (the one in Documents\Electronic Arts). These files should be deleted regularly anyway, and while you're troubleshooting, every time you quit the game. For reference, they are:
Then load your save, let the game clock run for a few minutes, and use "save as" to rename the save. Now you'll have a backup in case you need it later. Go to Edit Town and evict the affected sim from your active household; you can split her and leave the other sim in place. As long as you put her back in the house without leaving Edit Town, she'll keep her job and relationships, although she'll lose her promised wishes and opportunities. After you're done, save, quit, delete your cache files again, reload, and see if your sim is fixed.
If the above doesn't work, go to Edit Town and evict both sims. Then save their house to the bin, bulldoze the lot, replace the house with the saved copy, and move them back in. Save, quit, delete the cache files, reload, and test.