Compels come from the GM not NPCs.
New High Concept: Rogue Summer Knight of the CrossAlso, I don't think that your sponsor has to spend fate points to compel you, its part of the whole, "I give you power, you do my will" kinda thing.
The only exception is sponsor debt.
However, once they break the wrong sort of oath (and I'm inclined to think that the mantle of a Knight of the Faerie Courts probably qualifies as one of these) the sponsor gets to compel them a certain number of times without spending fate to do so.
Compels can come from NPCs. Exactly the same way that they can be done by PCs.
If you are aware of and can access an aspect on another character or NPC, you may spend a fate point to try to trigger the circumstances of a compel. If the GM decides this is a compel worthy-circumstance, then she takes the offered fate point and proceeds with a compel, running it as if she initiated the compel herself (YS107).
So I guess if the GM wants her NPC to initiate a compel the GM can have a discussion with herself and pay herself a fate point if she decides its compel-worthy and then she can run the compel as if she herself initiated it and offer that fate point to the PC. Life is really too short.