Sure, under the most simplistic definition devoid of any cultural context or connotation. But if you have to prune all meaning from the word to prove your point then perhaps your point is rather weak to begin with.

To put it another way: if your definition of sexism means that women-centric events designed to foster interest in an otherwise underrepresented field is considered sexist, then its your definition that is faulty.

Here's a definition that doesn't strip the salient context from it (dictionary.com)

1.attitudes or behavior based on traditional stereotypes of sexual roles.

2.discrimination or devaluation based on a person's sex, as in restricted job opportunities; especially, such discrimination directed against women.

It's amazing how these discussions always devolve into cherry-picking definitions and parsing language like a machine to prove respective points. If you have to resort to that, then just bow out gracefully as you are missing the point of the discussion altogether.