Got into a situation where Mimi was in the party, but her event chain did not trigger. Here's why: never got her friendship high enough in combination to walking back to Alanya. I always warped back or rode the carriage back to Alanya, but she was never in the party when I walked back. I was in Arland for quite a while. There's a "full basket" requirement

Source that helped (spoilers): https://gamefaqs.gamespot.com/ps3/991771-atelier-totori-the-adventurer-of-arland/faqs/63157#section39