Bringing it here:
Don't forget that if your purpose is to use it in your Talisman (and gain the benefit of the virtue) you must enrich the item of virtue yourself.
Why not retcon the amount of vis? At least to have enough to bind Lencor down the road?
Celeste did a sizeable amount of exploration, this could result in a reasonable harvest.
Other than that, maybe she receives a parting gift from... whoever? Items, books, spells? If books or spells this is a boon to the covenant as much as for Celeste, so maybe Tugurium could offer her some compensation?
EDIT: in light of my last comment on the Table Talk topic.
- If Ferra dissolves Collem and moves away, maybe she leaves some inheritance to Celeste, who while not being an apprentice was the last person to learn from her? This could account for a sudden influx of vis/items/books. Ferra did not have any official apprentice, according to TtA, so there's no one else to inherit anyway. Celeste might be a good candidate in the eyes of an old Bonisagus.
- If we go with Collem as is (entering a second spring and walking towards the point described on the book for 1220), maybe Celeste did gain a few pawns (retconed in her previous explorations), but those are gifted to Ferra to help her with the second spring in exchange for Collem Leonis approving of us joining Rhine (and Celeste being properly compensated either by Tugurium upon joining or by Ferra in a couple of seasons).
These are just random toughts, for your appreciation.
But it maches the established timeline. Imagine it: we are at the Tribunal, first order of business is to vote on Ferra's twilight (it was seven years since she was last seen, ), she suddenly enters the Forum of Hermes and says "no one go declaring me on Final Twilight before it's my time, you hear it!?!?"
And after the brief commotion, she votes for us. Maybe. 