This will be kinda long so please stay with me! I really need some help!!!

My problem starts off a few weeks ago when I had to be taken to L&D; for some complications. I'm a SAHM and I needed somebody to watch my 15 month old. I called my MIL and she was working but she said she could call her mom (Mimi) because she could get there quickly to pick him up and that she would go get him as soon as she could get free from work. Cool nbd. Mimi gets to our house and by this time my husband was home to drive me to the hospital. He gets CJ's car seat strapped into their car and says "do not let my mom leave your house without this car seat!!!" She has a car seat in her truck for the older grandkids, but cj is still rear facing and we are very strict about it. And my MIL is one of those that thinks "it's just a few blocks, it'll be ok"

Well, later that night when I get the all clear to go home, we go to my MIL to pick up cj. I asked my husband to get his car seat put back in our car so that we could go. He goes to his moms truck.... no car seat. He asked where it was and she replied "idk. I guess it's still with Mimi" I. WAS. LIVID!!! Sooooo, strike #1. So that right there tells you that she doesn't care to do what we ask of her with OUR child.

Onto my real issue.. strike #2. a while back we asked our families not to post pictures of cj on their fb pages. We post them, but we also control who sees our stuff. We can't control who everyone else is friends with. I had lunch with my SIL yesterday (she's married to my husbands brother so she understands my problems with our MIL) and I was talking to her about it because it got brought up with my in laws again this past weekend. She said "sooo, even after you asked her again not to post anything, she put his picture on fb???" I had no clue what she was talking about. She had to explain... Apparently, my MIL has been posting pictures of cj but blocking me and my husband from being able to see it. I brought it to his attention last night and showed him screenshots that my SIL sent me. He's pretty upset about it. I'm mad. I'm hurt. But most of all, I feel disrespected as a parent. We are trying to figure out how to approach the issue with her and what we should do. If it were completely up to me, she wouldn't get to see my son AT ALL! But, my husband doesn't necessarily agree with that...

How would you guys handle this situation?