I remember it having a girl who everybody wants to kill, as well as her guardians. It took place in what felt like a middle-ages universe, but it ended up being post-tech after some sort of apocalypse happened. One of the recurring characters was an AI.
This sounds like Scrapped Princess:
Where the girl that everyone wants to kill is named "Pacifica Casull", the "Scrapped Pricess", and her 2 guardians (a brother and sister). The story looks like a fantasy world but it's actually set in the future. When Pacifica reaches 16 years of age, she's supposed to cause the world's destruction so everyone is out to kill her. In the show, there are these things which are A.I. weapons systems, called "Dragoons".