Toxic mother in law issues

hi ladies, looking for some advice if you have been in my situation. Did your relationship with your husband’s mother become strained after children came into the pic? I think part of the problem is I didn’t really know her well before because we didn’t interact much but now that children came into the picture, I put some boundaries in place from the start and she did not take it well at all. And ever since that day she has been doing subtle things to create a toxic environment for me; such as stating that she will purchase car seats to drive my newborn around, will be taking them for sleepovers at her house, continuing to let them play with magnets (all things I have made clear I am uncomfortable with).  We have other issues too that came to light like she will be kind to me in front of my husband and other relatives but cold to me when it’s one on one, and if she is ever in the wrong and I bring it up she will play the victim or completely gaslight as if I misunderstood, etc. would love some examples of what your MILs have done and how you’ve handled them.  The major issue is that a lot of what is does is subtle and only seems to be evident to me. PS she only has one other now ex-DIL who cannot stand her because of similar issues.