Actually, holy shit, that sent me on a terrifying-slash-brilliant tangent.
First of all, Shinobu could sign a contract not to compel allies without their consent. For bonus points, one could use esoteric models such as Coherent Extrapolated Volition, because the computation of the contract runs by magic, and so may not actually be computationally bounded. CEV, for reference, is "would the hypothetical perfectly-informed version of you give consent." She would love being magically stopped short of issuing compulsions unintentionally.
Second, those who have been witchbombed/lichbombed could sign a contract that prevents them from disclosing it unless those they are disclosing it to could safely accept it. You wouldn't even need to explicitly name them in the contract; you could simply refer to "cognitohazards endemic to Puella Magi" and have everyone sign it, even before being informed. This would allow Reiko to draft it without getting bombed.
