MIL is crossing the line 😤

A bit long but I need to vent:

Let me start off by saying that my MIL and I have always had a good relationship. I didn't have a mom growing up and she never had a daughter so when I started dating/married her son we became very close. We have a 14 yo daughter and 8 week old twin boys. 

She lives literally a mile away from us and is here every single day whether it's announced or unannounced. These are the main issues I have:

•  She has slipped up on numerous occasions and called herself mommy to the boys. That was a fear I had when pregnant that she would instantly think that my twin boys were just like the two boys she raised and try to replay her parenting on my boys. She's constantly posting on facebook about how they're "her boys" and "my babies" and "my miracles" the my miracles part really gets to me because that is what I call all three of my kids since it took so long for me to conceive due to my infertility. It's always been a special thing ive referred to them as since having my daughter. 

• When she's here she is always taking over. She demands to feed them which I wouldn't mind because the help is nice. However every time she feeds one they spitup all over when they're done because she refuses to listen to me on how they need to be burped and she never keeps them still or upright which is crucial with their reflux. When burped and held properly they never spit up for Dad or me. The spitup isn't just normal spitup either it's out the mouth and nose which ends up making it difficult for them to catch a breath and they start panicking until I suction out their noses. 

• When she shows up she instantly picks one up and wakes them up from their naps. They both have colic and hardly sleep from 3pm - midnight/3am, so their naps are very important and much needed. 

• I've asked her to not post my children's picture publicly on Facebook. I did it in a very nice way and explained to her there's family I'm disconnected with that I'd rather them not get updates and I definitely don't want strangers seeing the pictures. There's people (her friends) that share these pictures and updates so that leaves more people I don't know to see them. She agreed not to do it anymore. An hour after I asked her not to do this anymore she posts two more separate status updates with pictures publicly. I was livid. 

Am I just nitpicking too much or would this upset you as well?? I'm going insane over it and don't want to lose it on her but I'm seriously about to. How would you address it if at all? My husband is very non-confrontational so he would rather not talk to her about it and thinks I should let some things go. Please HELP me figure out what and how I should handle it!