Or maybe she hasn't been paid, because her content did not receive the deserved attention when she released it.
It's only complex if you are a bot trying to solve this for maximum profitablility. I don't see what's actually complex about it. The "increasing overhead" could easily be addressed in a few months/years if statistics show, that too much Steem is paid to an increasingly huge amount of older posts. Also there should be a recontribution of Steem not used by inactive authers that haven't logged in for more than 6 months or something like that.