This is homebrew Casandalee lore, but it's focused more on lore than rules, so this seems like the best place to put it. I just saw that we'll be getting more information on Casandalee in an upcoming book, but my GM needs a justification now for how my PC knows about her, and why he would accept her as a patron deity.
----PC Background----
I'm in the middle of leveling up my Gnome Chirurgeon Alchemist to level 2, and Poison Resistance as a class feat seems underwhelming. Looking around at the multiclass Archetypes in the core rulebook, I settled on the Cleric dedication, but my PC isn't a particularly faithful individual. The driving motivation that I built my character around is that he wants to build a mechanical suit to give mobility to his disabled keenspark gnome 'sister' who is in danger of becoming a bleachling, and Casandalee has access to that kind of technology. He already had long-term goals of going to Alkenstar and the Silver Mount, but hasn't ever visited either.
----End PC Background----
My headcanon:
As a recently-ascended AI demigoddess, Casandalee is preferentially recruiting organic followers who will promote harmony between artificial and organic intelligences, which will open up more opportunities to recruit followers who will advance AI in the future. Her success in Numeria has been limited as most of the technologically adept individuals in the region were members of the Technic League (which she helped destroy), and technophobia prevents many others from being willing to follow an AI deity. As a consequence, she sent out cloaked observation units to major population centers around the Inner Sea to find potential candidates for extended observation. If the candidate exhibits altruistic tendencies (Love), acceptance of societal outcasts (Reaction to Unity's xenophobia), and an interest in science and engineering, the observation unit approaches the candidate in private and plays an interactive hologram of Casandalee offering a personalized incentive to join. Upon acceptance, the spine of the new devotee is augmented by nanites to be an antenna for transmitting 'prayers' and receiving spells and blueprints, and additional minor modifications are made to cast cantrips powered by the cleric's Intellect.
Having observed the perpetual turmoil and reactive technophobia caused by the dissemination of weapons technology in Numeria, Casandalee will only share defensive and medical technologies with new followers. She wants them to exhibit the benefits of interacting peacefully with AIs, and is actively seeking to suppress the spread of advanced firearms while supporting Golarion's natural technological progression. Knowing that many of her followers would not have access to the Divinity's facilities, she encourages her clerics to modify blueprints to create lesser modules and subsystems held together by magical duct tape and mechanical bailing wire. Crafting advanced healing, defense and support systems such as a medi-mech or low-profile power armor requires a pilgrimage to the fabricators of the Silver Mount.
As the scattered Technomancers of Numeria become aware that Casandalee is sharing new technology, they will prefer to capture and interrogate her devotees, but will resort to assassination if that fails.