One of the things I love about the Lord is that He doesn't let our traditions get in the way of His love for us. I am a Protestant and therefore don't embrace Catholicism's deep love for Mary. Although, I must admit that "The Passion" has caused me to emphasize with her much more than I did before, and I don't think that is a bad thing.
But, whether we Protestants agree or not, Mary is a big part of the Catholic tradition and I have a hard time believing that God would have problems with their love for her. In fact, it more than likely blesses Him. Therefore, it is quite reasonable,in my opinion, to assume that He would use these Marian miracles to bless and encourage those of the Catholic traditions. Perhaps we Protestants are missing out on these miracles because of our predjudices.
As far as some of these Marian miracles being demonically inspired, I believe that that is probably happening, as well. When we examine the revivals of men like Finney, Brainard, Whitfield, Edwards, et al, we read documented accounts of many miracles that drew people to God. But, we also can see many false miracles that caused confusion and division and eventually could be considered resonsible for snuffing these revivals out. It would appear that satan won in the end. But, it's not that way really. Thousands of people gave their lives to Christ before the devil got a foothold.
Really, we see this same kind of thing happening today. I sometimes don't think it's evil spirits as much as the human spirit that gets in the way and ultimately snuffs out the work of the Holy Spirit. Most every church is started with revived hearts, love and joyful worship. Then man gets in the way and turns it into stone, brick and steel.
I really feel it grieves the Holy Spirit when Christians begin railing against other Christians just because their experience with God is different that their own. God has to deal with galaxies imploding on themselves on a daily basis; don't you think He is a big enough God to work through our individual theological understandings of Him and still love us and perform miracles? I do.