Is an brother's reprimand of his sister for two major mistakes, after remaining silent about the first, considered a flaw for which he will be afflicted?

Your duty was to condemn the wrong and advise the one who committed it. It is not permissible for you to shame her for the sin. Imam Malik said in al-Muwatta: "Do not look at people's sins as if you are lords, but look at them as if you are servants. Indeed, people are of two types: those afflicted and those in good health. So, have mercy on the afflicted and praise Allah for good health." Condemning the wrong is not considered shaming.