SM Stirling's alternative histories include the canonization of two historical characters known to us: St Disraeli and St Diana, the latter being the deceased first wife of Charles III. These latter two are not proclaimed by any Pope but are perhaps canonized on the Vox populi vox Dei ("The voice of the people is the voice of God") principle.
In our history, Charles I is canonized by the Church Of England as "King Charles the Martyr" - though not in the timeline of Anderson's A Midsummer Tempest, where he was not executed.
In a timeline prevented by the Time Patrol, Veleda would not have become a saint, because she was not a Christian, but would have been recognized as a sibyl or pagan prophetess.
If you enjoy reading these posts half as much as I enjoy writing them, then you are very happy people.