Like Ben.Dover said, you can change your choice if you have previous 'persistent file' (before you choosing a choice) which automatic generated in your save folder. if you have this one, you just need to replace this file to your save folder in your game folder and in %appdata%>renpy>lustfuldesire... (This one is automatic backup, games which developed by Ren'py usually automatic generated this folder to contain your backup save and persistent files)
Warning: persistent file is a very important file which contain a data of your game play like dialogues you have been read, a choice you have been choose. So it may cause some bug when you replace the old one to the new one.
P.S. This is a method in PC version.