After reading the chapter comments, it turns out the female Thor lifting the hammer has nothing to do with Thor.
I thought I might have remembered it wrong, so I went back and reread the Original Sin event. The comics clearly detail exactly how the new Thor came to be.
The story goes like this; Nick Fury manipulates Thor into doubting whether he's truly worthy of Mjolnir. As a result, Thor genuinely can't lift the hammer anymore. Then Jane Foster, who is battling a serious illness, senses the hammer calling to her and lifts it without any trouble.
When Thor realizes what's happened, he storms over in a rage, accuses Foster of being a despicable thief, and tries to fight her for it.
In other words, the first meeting between the two Thors only happens after Foster has already become the new Goddess of Thunder. There was never any moment where she needed Thor's permission or blessing to lift the hammer. That never happened.
On top of that, Thor wasn't in any position to grant blessings anyway. Even using the same Mjolnir, the female Thor demonstrates far greater power than he ever did. Thor himself admits that the hammer never showed this kind of raw, explosive force when it was in his hands.
It really caught me off guard. I was worried my memory had failed me and I'd written something incorrect. Also, for the record, the protagonist's starting universe in this story isn't Earth-199999.