Cordelia's Ending event requirements:
Cordelia has some high value requests she submits to Esty, which are not marked as friend-requests. These are random, and I'm not sure if there is any specific timing or triggers to get them to show up. Some people, such as myself, have had issues with having them show up. It is not uncommon to see one in year 1, and not see another until year 3. Completing her friend requests do NOT count for this.
Iron Clay x2
Cotton Flower x2
Glow Sand x2
Sunny Crystal x2
Mont Blanc x2
Shadow Grass x2
You do not need to complete all of these. I've only seen Pebble, Iron Clay and Mont Blanc myself. The same items can show up multiple times. You will recognize these because the reward is absurdly high, and you will lose some town reputation for completing them. I have only heard of Mont Blanc requests showing up in year 3. These requests may not show up at all during Assignment 12, so try to do them sometime during Assignment 10 and 11.
Other events for her flag:
- After 2x Pebbles, there is an event with Esty, Rorona & Cordelia.
- Event at R&T when Cordelia's FLV >= 60 and you have completed 3 requests
- After the previous event, fail a synthesis to obtain an item you can give to Cordelia. This might not work until Year 3, Month 7 or later
- Complete a 4th request to get another event. Cordelia will be unavailable for awhile. Talk to Esty.
- 10 days after previous event, another event when leaving the workshop
- 10 days after that, the final event will occur. This also unlocks the Making Up trophy
After assignment 12, select the True ending with Cordelia to unlock this trophy. The true ending requires a lot of stars on the assignments, more than 100, and town popularity over 80%.