People cannot be revived as they are deleted as soon as they are dead or removed from all slave lists. There are a couple things that could be cleaned up such as removing that dead person entry from relatives data, which involves searching for the entry that matches Emily's ID, but changing the quest line state is quite simple.
The save file can be accessed from the Mansion's Save/Load menu, which has a button to open the save folder. The save files are plain text files that use the JSON format, but they do not have any extension so many editors won't recognize them even if you have something to handle the format. Either way all you need to do is find the entry that looks like:
"emily":16
(It could have another number like 101 depending on how you acquired Tisha) Then change the number to a 14 or 15. Save the file, load the save in Strive, and go to the Gorn slave market to collect a new Tisha.