In the first two seasons, she had conversations with and addressed Amanda several times. In season 3 and 4, and the webisodes, she forgot Amanda's name and at one point didn't even know who she was ...
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How do you know if you're happy or sad without a mask, or angry...or ready for dessert
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As bitca360 pointed out, Wilhelmina didn't care for the "little people." The only assistant she managed to remember was her own (Marc), and Betty sometimes. Remember the episode where Betty won the BLOBBY award? The BLOB representative showed up to interview Betty and when she saw Wilhelmina, she approached her to invite her to the ceremony? Willi mistook her for Betty even though at this point she had had several encounters with Betty.
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