I haven’t used the chat extension which you got from the other thread, so I can’t comment on the specifics of that.
But you could, for example, introduce and set flags (booleans / truth states), so something like this should work:
Greeted-Westley is a truth state that varies.
Instead of talking to Westley:
if greeted-westley is false:
start a conversation with Westley-hello;
now greeted-westley is true;
otherwise:
start a conversation with Westley-cic;