So here are some thoughts on a screening process for 'new residents'.
Magical Girls wishing to immigrate and live under Sabrina's promise of keeping their soul gems cleansed have to agree to the following:
- Full disclosure of their powers and any ongoing wish effects, though they need not talk about the circumstances of their wish if they don't want to.
- Full disclosure of their histories as magical girls. That is, people they have been on a team with, people they have fought with... people they have killed. This is Confession time. All will be forgiven and the slate can be wiped clean, but only if they confess now. We don't want to be caught off guard by an unsuspected grudge.
- A one-on-one interview with Sabrina or someone she designates to carefully ascertain their Lich-Bomb/Witch-Bomb status and warn them about memetic exposure to girls not cleared.
- Agreement that Mami is boss and will be the final word on any magical girl disputes. (Though I suspect many will conclude that Sabrina is the real power, given that Sabrina is the source of cleansing and that Mami obviously dotes on her.)
- An understanding that those with useful non-combat wish magic may be called upon to pitch in as needed to help build lives for everyone.
In return they get:
- Sabrina will clease their soul gems regularly. (Until clear gems are proven safe, they should not be an explicit part of the deal.)
- Prior crimes, up to and including murder can be forgiven under a general amnesty. (A show of remorse is expected if there are any victims also in residence.)
- They will be aided to set up new lives.
Because the first immigrants are the desperate they will agree to this, and later immigrants will be under pressure to agree because everyone else already did.