Friendship question can someone explain

I have a couple of mom friends who when we go out, we don't totally communicate and I assume we just look out for or own and share a bit when we meet (resources snacks etc) but sometimes we butt heads esp when they always offer food to my son and I'm like FFS..like I have my own. I'm trying to build healthy eating habits, not shove food in their mouth all day long. Like my son will tell me when he needs a snack. And so I say no thank you it's like the air changes and they get offended by my no thank you. Like he just had a snack and dinnertime is coming up but it's like I can't have my own rules. They override and push my boundaries. I don't like it. Wtf is this and I don't feel comfortable around them all the time, it feels fake but I'm not sure because I have gotten this wrong a lot. I'm often confused and we're not always on same page and it's so annoying that I can't have boundaries and respect. I think I'm communicating clearly but it's them who don't read my texts or anything 🤷🏼‍♀️