Why do you have to make it about her sex/gender? It is completely irrelevant to the topic at hand. You don't know why she is in this position and making this mistake. What you do though, is derive something solely from her sex/gender. This is helping no one and only perpetuating useless stereotypes and hatred. Please consider not using this argument and instead just say: 'Why would she be saying this? There is no reason to call Dota 2 a newcomer, when DotA-Allstars is what was the birthplace of League of Legends? Since Dota 2 is nothing but a follow up to DotA, it is at best misleading to call Dota 2 a newcomer.'

This way you do make your point, that you disagree with the statement in question, instead of just insulting the person making the statement based on some superficial stereotype you have and reproduce.