So, the explanation is implied in the last strip, but perhaps not fully explained, since Aylia didn't need everything spelled out to understand it.  All witches, in Aylia's world or out of it, have familiars, which act as a focus for magical power.  A witch and her familiar are always connected, even if they're far apart or one is currently incapable of using magic, so Jocelyn was able to order her starfish to cast magic for her.  That wouldn't work for anything too complicated, but transportation magic is straightforward.



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