You are saying that islam isn't fair and just as well as all religions,but are you sincere with yourself to be a muslim while you believe that all religions including islam is unfair and unjust,i am just wondering.
i do really respect and honor the atheist when he make it clear for everybody that he doesn't believe on any religion,at least he is sincere with himself.
While i don't agree with her statement that Islam is not just, but you don't have to question whether she is a sincere Muslim or not because you don't have the right to do so. if she feels Islam is not just, fine, either keep quiet or ask her why she feel so if you disagree. Many Muslims can be civil with non-Muslims but they can't do so with their brothers and sisters in Islam.
She sees how you behave then you wonder why she think Islam is not fair and just?
Don't you know that most of people see religion through the actions of those who adhere to it?