Kanaya can magically perceive the threads of space, recognize what they connect to, and manipulate them to create dimensional bridges between the things connected to them. This essentially grants her telekinesis and teleportation.
Each person has a thread leading to them, but some will certainly not be fond of having theirs plucked or tugged, and Kanaya certainly wouldn't be so rude as to disrespect those wishes. That's why there are permissions posts!
There are three main questions here
~ Recognition, whether Kanaya can look at your thread and know who it belongs to
~ Interaction, whether she can interact with that thread to whatever effect (will only be done with permission for each instance, of course)
~ Teleportation, whether Kanaya can drop in on your character without directly playing with their individual thread
i'm pretty okay with whether they have an ic protection against her magic or just an ooc inclination that this should be generally avoided, whichever one you have