Complete all the quests with the brunette nun and then invite her on a date.
Use the cheats to unlock the blonde nun halloween scene. You need a code for that. You can find it here: https://www.patreon.com/posts/cheat-codes-41816134
Viewing post in Knightly Passions [1.21 version] 18+ comments
Play the 0.5b version. Date her from start if you have a previous save. And now meet her after morning, invite, tap the hug option. Next day at same time invite, kiss, again next day, invite, vaginal, next day, invite, vaginal+anal, next day, invite, extreme option. Do this in one game session when you play. If the bug stills persists, wait for the next update around the end of September or early October.