There are rules against Pandora throwing the first punch, but she's allowed the second. That's probably not an opening one should give her.
Granted, she attacked Magus, but Magus has been stuck n the unenviable position of not enjoying the protection most people get from immortals.
Grace did agree to a plan to help her remember The Emissary's warnings, so he might not technically be trespassing anymore. On the other hand, Grace was literally asleep when she agreed to that and has very little memory of it, so one could argue that doesn't count for much.