For more context, I opened my save in a save editor and found 4 relevant flags (excluding the ones that have to do with the Nastizia route or her quest).
Those being:
RIYA_PUNCHED
RIYA_SUSPICION
MET_RIYA
RIYA_TALK_HUM
I've tried setting RIYA_PUNCHED to 0 or 1 from it's original 2 which only allowed me to view the last dialogue you get after punching Riya. I've tried to change all the other flags mentioned here to zero just for good measure which also gave the same result. After viewing the flags of a save file from an old version where I didn't punch Riya, I noticed that the RIYA_PUNCHED and RIYA-SUSPICION flags aren't present. Which leads me to suspect that the solution to my problem might be removing the flags entirely from my save file. However the online save editor I was using doesn't support that, and I can't find a save editor program that works.