you might have run into a fringe case where your values are outside of defined parameters.
Bleh, looks like twine decompiling and save editing is in the forecast then
UPDATE: No, that's not it at all. The only criteria checked as to whether or not to proc the event is whether it is October 10th or not. The chapter 3 trip to the steak house _always_ procs on October 10th. And once at the steakhouse it only checks how many times she's been dosed along which path... "s5" in my case. And, it so happens, "s5" is an empty block. Hence the lack of any option to proceed.
This _does_ however, indicate that the number of times you can actually dose her is not tied directly to the number of opportunities one has to dose her. Assuming Westane intends for there to be more opportunities to dose her than there will be actual doses... then you could potentially miss a few chances to dose her and still end up with a completely dosed Sophie by the end. As is right now, there are 5 chances to dose Sophie and only 4 doses have been programed in.
So I guess if you have dosed Sophie four times before Chapter 3 starts, you're better off skipping the Chapter 3 Steakhouse opportunity.