Attendant to their lore as manifesting from the souls of dead children (Along with the Fuarth being souls of the drowned), it could be the pull of the Lifestream on the First is significantly less strong than on the Source.

They don't physically manifest anywhere other than the First. Feo Ul does what she does through Dreams. Your pact allows her and her alone to bridge the gap and experience the Source through the Dreams of people close to you.
Tataru says that Feo Ul appeared to tell her about you while she was in the middle of working.