The same thing happened to me after I spoke to Duncan in Chapter 1 — I got a second Aire, too.
I chose the slave route with the princess. First, I obtained her heirloom bracelet, and then I convinced Aire to help me find Anastasia.
Aire(s) also seem(s) to be counted as a regular character (white name), rather than a unique one (yellow name). I can sacrifice her for stats, and so on.
Resurrection spells also stopped working.
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