How to stop my catholic mother in law?

I’m atheist and my husband is more spiritual than anything. Before we had children, we both agreed that we would raise our children without religion until they are old enough to fully understand and choose whatever they believe in themselves.

Wellllll, my mother in law is a hardcore catholic (nothing wrong with that) and she is constantly trying to shove her beliefs onto my son and myself. She knows my beliefs and doesn’t respect them at all. She is always saying things like, “oh god gave you such a beautiful child” when she knows it upsets me.

I’m fine with her beliefs and I respect them fully, so I feel she needs to respect mine. She is always trying to introduce religion to my son behind my back. Even tried to hang a cross in his fucking nursery. This is not okay. My husband and I are his parents and we need to be respected. How do I take care of this in the least disrespectful way possible? I love her but some of the things she does makes me want to pull my hair out.