I'd probably ask your partner to have a word with her if possible. Ask him to let her know something along the lines of that you have researched today's reccomendations before making choices for your baby that work best for you and your baby what youre comfortable with. That while you appreciate 🫠 her experience that reccomendations change and if there is anything you would like advice on you would prefer to ask for it as needed rather than her always giving it unsolicited and making it feel like she's questioning and being udgemental of your parenting of your own child. Maybe that while you're happy to talk, these are not the topics you want to discuss. This is the rough message I had when I was ready to fight someone on this but also wanted to try not cause more friction 😅
At the end of the day it's your baby, you know best and you're the decision maker. But as her son your husband should really be sitting he down for the hard talk. You're not the a hole, it's hard not to be pissed if you're constantly receiving this. I really hope it can get better and she can start respecting your boundaries, it seems to be a really hard thing for the older generations 🙈
No I don’t think you’re being an asshole. Unsolicited advice is annoying from anyone, especially if they are constantly saying you are doing something wrong. Guidance on raising children changes every few years, let alone the decades since your MIL had a child. You can raise your child how you want and the people in your life should respect that. If they disagree, there is a way to talk about it and educate themselves on why you’ve made that decision rather than being judgemental. Has your husband spoken to her and said that she needs to respect your parenting? I think grandparents tend to listen better when it comes from their own child