[Tezcatlipoca]

Could be the same person, and the Doctor encounters her earlier on in her timeline or somehow stops her getting converted.

Or it could just be that the characters are related, but played by the same actress. That has been done twice before:

Freema Agyeman first played Adeola Oshodi in "Army of Ghosts", before later playing Adeola's cousin Martha Jones.

Eve Myles first played Gwyneth in "The Unquiet Dead", before later playing Gwen Cooper in Torchwood. Although not officially related, they of course looked identical, which Davies claimed was due to "spatial genetic multiplicity" caused by the Rift.