If God's dishing out the blessing, then he's dishing out the curses. Most of the time Christians tend to focus on one aspect of God's characteristics, which is often his great love. Sure it's, good, he does love, but he also had many other traits, be it justice, mercy and hatred. Yes, he does hate, specifically sin. Even the 'Christian God' loathes sinful behavior, and he loves the sinner though. If God's to blame for the good, he's to blame for the bad.
I don't think you really understand what a 'curse' is. Think of it like the opposite of a blessing. A curse from God is not like some sensationalized, witchcraft, business like what you might see in a movie. In no way are you enslaved by God's curse, we can do all things through Christ, including 'getting through' a curse from God. Through suffering, character, perseverance and hope is built. This is just how life works. God never allows us to be exposed to a temptation we cannot overcome, and we always will overcome it with God's help, despite how bad it may seem.
I think it's been mentioned that yes, that Exodus passage was overthrown. We're no longer under the curse of the law through the blood of Christ. However, we're all still cursed with a sinful nature. It's not something people enjoy talking about, but many believe God curses family lines, I do too. Children tend to mimic the behavior of their parents. So, if a child is exposed to a violent parent, they are more likely to be violent themselves. The same applies to alcohol, drug use, divorce, religion, unhealthy eating, finances, etc. It's human nature of behave like our parents and some of these traits just get passed from one generation to the next and the next. Ha, generally it take 2-4 generations before we see improvement. Some people also believe illness, mental or physical, are sometimes God curses upon our family line. And we brought it all upon ourselves, under God's permission, that's sin in action and that's its ugly consequence upon us. We're not cursed by God's wrath towards our sin, but by the very nature of sin itself.
Now, is God mad at your mother because her great grandfather stole something? No, I believe someone here even brought up some passages. It's her sin alone that God is judging. God loves expressing his great mercy and forgiveness upon us, and he blesses those who obey his commands. If your mother feels as if she's being cursed by God, she could very much have some sins she needs to repent from. Or God could be exposing her to hardship to increase her faith and such business. I have no idea, God doesn't ask permission to do things. It may sound silly, but she should probably just ask God what's going on and reaed Psalm 18. It's way too long to quote.