I have been having problems with my family recently, mostly stemming from my brother's new wife who has, since her marriage, become increasingly antagonistic toward us.
It is now at the point where she is outright cursing me and my family — while she is reciting the Qur'an, no less — and even my own brother has started to turn away from us. I am worried that these curses may actually be taking effect and causing discord between us.
I know that cursing does exist in Islam; there are mentions of the curse of Allah being upon various peoples in both the Qur'an and in the Sunnah. What I am unsure about is whether or not these curses can be invoked by anybody.
Is my concern valid; do my sister-in-law's curses have any power over us? How can I be sure that my brother and I (and the rest of my family) are not under a curse?