The magic is available as soon as the ceremonies are preformed. You'e made your sacrifices and then you're been gifted with the magic (probably starting at a 12). I don't see any reason why an Ernaldan would lose her other affinties -- Red Woman looks to be an Ernaldan subcult but I'm willing to be wrong about that. Certainly she'd get them back as soon as she was done.
Hope this helps
Jeff
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