My parents have a few deeply held but uncommon and bizarre beliefs/principles that are very much part of their lives (not in any way related to religion). I was brought up on the fringes of an almost cult like community which I consider now to be quite toxic and avoid as far as possible. Apologies for being a little vague but it's a) outing and b) likely to derail my actual issue if I'm more specific!
Anyway for a long time I genuinely believed some things that I now find myself questioning and have started to do things differently with my own children. Up until having my last child I did things the way my parents had but over the last 5 years I've had some realisations and have made some changes to our lifestyles, which I haven't bothered discussing with my parents as I know it will lead to probing and questioning and constant comments. I cba with all that, part of the reason I left home at 16 was that I'd had about enough of not being allowed even mental privacy and being expected to discuss things at length that I wanted to keep private (eg my mother always insisted on me telling her when my periods were due which I'm sure she thought was a reasonable thing to know but I hated having to tell her).
Anyway my oldest child (now a teenager) is very close to my parents as I was quite young when he was born and they were very involved in helping me out for his early years. My parents are loving grandparents and have a great relationship with my children but I do keep them at arm's length from certain aspects of our lives, especially any medical or health information which is one of my parents specific idiosyncrasies.
My oldest child has mentioned a medical treatment to my mother which she disagrees with and refused for myself and my siblings. I don't ask my DC to keep secrets from people as I believe it to be damaging but I assumed he wouldn't bother to mention it as he knows what their beliefs are... I assumed wrong but that's life and obviously I don't hold my DS responsible at all and will not be telling him about what's happening as a result 
My mother has been on the phone to me and has told me in stony terms that I have "misled her" and "damaged our relationship" and that she only "bothers me" because of my children and won't impinge on my life any further and that she's leaving all future contact up to me.
I'm left feeling like the teenager who got no voice or privacy. I'm raging. She's not a bad person, in fact in many ways she's very sensible and sound. But she has these bizarre beliefs and is taking my silence on the issue over recent years since I started to see sense as continued agreement with her.. but actually I was trying to avoid exactly this scenario!
Not expecting any advice really just venting and trying to make sense of it all and where to go from here.