Note that you've gone from "It is not clear to me that it is sexist," to "She is wrong about the explanation."
That something isn't clear to you only means it isn't clear to you. She is in possession of an enormous volume of information about the situation. You aren't. The reasonable conclusion isn't "sexism is a redundant explanation"; it's "perhaps she has not revealed the information the led her to her conclusion".
Now ask yourself: why did you so quickly leap to the particular erroneous conclusion that sexism was not the problem? There are a lot of erroneous conclusions to come to. Or you could have come to none at all.
That something isn't clear to you only means it isn't clear to you. She is in possession of an enormous volume of information about the situation. You aren't. The reasonable conclusion isn't "sexism is a redundant explanation"; it's "perhaps she has not revealed the information the led her to her conclusion".
Now ask yourself: why did you so quickly leap to the particular erroneous conclusion that sexism was not the problem? There are a lot of erroneous conclusions to come to. Or you could have come to none at all.