It's interesting that I happened upon your post, just after watching this video:
Stephen Dollins - Satanic, Occult, Pagan, and Witchcraft Symbols - YouTube
It made some interesting connections between learned attitudes and behavior and how they are influenced. The title doesn't really set you up for what your about to learn. I also found it interesting considering Stephen Dollin's history. It's very insightful in regards to what's going on with humans thinking all over. If you don't mind, I'd also like to know what you thought and if you've made other similar observations yourself? I believe that though Mr. Dollins is addressing current influences/inspirations, but also brings out that humans haven't changed; that we (society) have been inspired by various means, to do, say and write things to promote rebelliousness against authority in general, the same way Eve was deceived. She was convinced that she could make up her own mind and didn't really have to be under the authority of God, or even her husband, for that matter. Our general rebellious behavior is not new. We've been learning how to work it for a long time. If God inspired men to record his own thoughts and desires in the Bible to instruct us; Why can't Satan and Demons do the same thing to influence us to their way of thinking or buying something?
God gave us the Bible so we could learn and be aware of what is going on. So that we could know how to protect ourselves. Because there is no concrete strong enough, nor tunnel deep enough in the earth to protect us from a spiritual threat that Satan poses to us. His attack, is on our personal character, inside our hearts where desire comes from. It's a challenge to our faith and obedience to be the sort of people God wants us to be. Since our spirituality is reflected in our outward speech, thoughts, appearance...our every expression is either to glorify God or it's against him. If we fail to submit ourselves to God's council like your wife and mother-in-law seem to be, then God will see that we are serving another master.
Anyway, I think you will find the information in the video very interesting and may even help you understand or see things different, so that you'll know what you're really dealing with. Then by praying for God's Holy Spirit to guide you thru the Scriptures, you'll know how He thinks you should handle the issue. That's really the only way to make a Biblical informed decisions. You could get a spiritually mature brother to study the Bible with you to help you and for discussion. It's free. Not to mention, it really helps to navigate thru spiritual challenges like what you're experiencing. After all, you are the spiritual leader of your family and your daughter is ultimately your spiritual responsibility no matter what her mother does or says, your example is what God sees you setting and teaching your her when she is in your care and keeping. Your actions teach your daughter weather you are a man who is upholding what is right in Gods eyes or choosing to behave like a contradiction like mom and grandmother. Teach you daughter the difference between Truth and Deception. You start by showing her that you turn to the God of the Bible and using it for guidance and strength and are applying it. Kids are smart and they are watching, eager to learn.