What we know or can be fairly certain about
* If you attack Mab directly, she can kill you.
* If you are a random mortal, she can use her knight to kill you - but is unlikely to do so unless she has a reason.
* We do know that Aurora was able to attack Murphy ineffectually with the plant monster. Enough to cause some bruises perhaps, but nothing more.
* We also know that the same restrictions apply to any agent Mab directs to harm you.
Speculation
* I think the restrictions on her actions are quite severe or she would not need a knight. if all it takes is some illusion to manufacture a token offensive action against Mab, that would be child play for Mab to arrange.
* Equally sure, Mab can do all sorts of bad stuff to you that is NOT prohibited by this stricture. Things like imprisoning you for a thousand years in a block of ice... Yet that too seems a significant loophole. I wonder if Mab's actual restrictions are much more than simply a limit against killing a mortal.
* Ditto with selecting an agent which is likely to harm you "on their own" Seems a huge loophole.
My own personal feeling is that the actual restriction is much broader than simply killing someone. I think Mab is prohibited from harming directly or even somewhat indirectly any mortal that does not "choose" to involve themselves in fey business. This includes her taking actions that are likely to result in harm, even if she does not direct it. However, she is allowed to create conditions where an enemy feels motivated to attack or harm Mab in some way. But they must be in the wrong, not Mab.
