Nah, I think her exclamation was perfectly on point.
"Why do I have to hear this from you, someone I've never spoken to before?"
Although, personally as a guy in a country with less emphasis on politeness I feel like Alya was well within her rights to clap back with something even harsher. That might impact her image and the public perception of her suitability as Student Council President however.
Still though, I feel that glasses-girl here's audacity actually somewhat strains the suspension of disbelief. No way someone supposedly so high up in the student rankings (you need qualifications to run for Student President in any manga), would be so clueless, insensitive and rude as to publicly demand their opponent back down for reasons that boil down to "You're trading sex for success, new girl. Don't you know all the lore??"
Like can you imagine this in real life? I don't think I'd be able to control myself from firing back once I fully wrapped my head around the sheer audacity and ridiculousness.