Download the Universal RenPy Mod, extract and place the RPA-File in the game subdirectory of your game. After starting and loading a old game, you will be able to start the mod by pressing <ALT> + <M>. After the short message about the mod, the mod's main window should look like this:
At the right top, there are some chars (R P O U W), at least the char O should be green, R shouldn't be green but red. The other ones do nothing if enabled or not.
On the left top you will find the search bar, insert images_sexting_4xx (exactly like this, all lowercase as RenPy differentiates between upper and lower chars) and click on the search button. Now it should look somehow like this:
For me, Faye is the first one listed (could be other on your result list), if you found her, you can click on the small arrow showing right beside Faye's entry left of list in the column Value (is should say 2 items like in the pic):
Normally, is should show the indices of the pics which will be sent during sexting, Faye can send 2 pictures with the indices 400 and 401 (the numbers will be used in the code to address the right picture).
Take a look at this first, if the indices are missing, there could be a problem generating the arrays during initialization of the game. If not, we can continue to the next step of troubleshooting.
A small warning: PLEASE, DO NOT CHANGE ANY VALUES HERE USING THE MOD, IT COULD BREAK THE GAME. Use it only for others helping you, if you want to change values, use the mod on the initial post of this game.