LIke, I said, I have never heard anyone say that Immaculate Conception meant that God created her. I think what you mean to imply is you thought Immaculate Conception was something like the conception of Jesus, which is completely counter to Catholic teaching.
Now, were you taught this, or was it never explained thoroughly, so you drew the parallel?
Having had many years of catholic elementary and high school classes, I can say that this was the 'implied' teaching. Details were never gotten into. My interest in understanding religious teachings greater occurred later in life than when it was offered so I will take some ownership in this 'misunderstanding' of the teaching.