How can I convince my mother that voodoo isn’t real?

My mother has been calling a "spiritual adviser" for years now and it makes my sister and me very uncomfortable because we know very little to nothing about this adviser, though we jump to conclusions and assume this lady does voodoo. Even though we are not sure, my mother pays this lady 500 dollars when she talks to her. She claims there are no tarot cards or anything and she's from some Christian church. It just doesn't sound right to me. I tell my mother how I feel, and she tells me to mind my business and walks away. She listens to the lady, reads certain passages the lady gives her, and prays from certain Psalms. That's not bad, I give her that, but what angers me is that my mom goes to her for advice and pays money rather than going to God herself for free. As long as she's been doing this there hasn't been any progress. We are still struggling and she doesn't see that. Instead of giving this lady money that has done nothing for us, she should be saving it so we can move. I've been going to church for months now, I've been inviting her, and she has not come once yet. She tells me she's going to go. I tell you I'm going to go crazy with her backward mess.

My mom has been brainwashed into thinking people did voodoo to her as she grew up. We live with her mother, and she thinks it too, as well it being done to her also. Even though I've pointed out in the Bible what is said about voodoo and such, she doesn't believe it and feels when I get to a certain age I'm going to understand. Then I'm going to have to go to people to protect myself and my family because people are going to be doing things to me.

In conclusion, what do I do to help my mom snap out of both brainwashings?