At puberty, changelings receive “the call,” a hypnotic spiritual voice that beckons them to travel and discover their true origins. Changelings who ignore this call choose their own destiny; those who heed it discover their “mother” and may come into great power by transforming into hags themselves.
I just have three questions on this.
1) How do hags go about with this call?
2) How hard is it for a changeling to resist this call?
3) How would a hag react to a changeling resisting this call?
1) It's probably a ritual of some sort performed periodically by a covey, with the hag mother acting as the focus/primary participant ("blood calls to blood").
3) It would depend on the hag's personality and the changeling's circumstances. Some hags will track down their "stubborn" daughter for capture (and forced conversion), some will hold a grudge and (with fairy-tale logic) send various curses and torments (working "behind the scenes") against the changeling (and even her descendants), others will write it off ("the useless chit wasn't worth it, anyway") and move on to more pressing issues (although they may react differently if their paths cross with their daughter at a future point).