Perhaps not intentional sexism, but I'd say this is very real. Though I think she might want a new coach who isn't going to jump to conclusions.
It's hard to not be ageist, but in this case I think there was some of that "she's half my age so why is she higher ranking than me" involved.
But you're definitely right that there's not much evidence here. I can still make assumptions no matter how much of an ass they make me.