Does Aerin have anyone that just sets her on edge right away? Is she ever fooled by a first impression?
Aerin immediately hated Isolde. She’s pretty good about giving most people the benefit of the doubt but when Isolde showed up, pleading with Teagan, Aerin turned on the sarcasm and aggression from the beginning (she scandalized Alistair when they were back at camp by asking if Connor was actually Teagan’s son).
Zathrian had her hook, line, and sinker from the beginning. It never occurred to her to question anything he’d said until she met the Lady. That trust was mostly due to her bias towards the Dalish but also because her immediate thought was curse=bad, so of course she needed to get the heart to break the curse.