It's not that she's too big. It's that her proportions are 'unusual' to what agencies expect from a model to walk runways or model clothes. There's not denying that booty. The 'industry' looks for models to fit in the standard size clothing they produce for the runway.
I'm not defending the model industry, it's toxic nonetheless, but I do think that her outcry is a bit out of context. She's not considered too 'big' meaning fat, it's proportions. That said, she is absolutely stunning and I'm sure she can get modelling gigs. Just not within the branch that looks for models fitting a specific mold, where they are basically clothes hangers with an interesting face and walk, nothing more or less.