I had this from my baby's own dad, apparently I was depriving him and his family of the opertunity to feed the baby,
Quite surprisingly his own mother jumped in one day when he was being spiteful and told him in no uncertain terms that bf was best I was clearly doing well not struggling with it and he should thank his lucky stars I was doing my best to give our child the best.
She did ask several questions about additional water and amount of feeds but in her day that's what they said 4 hours between feeds and cooled boiled water in warm weather, she was also very quick to activity seek out info about current advice, in all other areas she was a bit weird and stalkerish ( not being unkind she was stalking us) but with that she was ace and it stopped most of the really anti stuff from dad.
Fil at first was a but unnerved but he soon got used to it.
My mum on the other hand whilst being openly supportive if asked makes comments like " so what are the current guidelines re length of time" umm same as when your other gc was born last year.
But her views on it chop and change depending on what other mums ( ones she likes more in the family) are doing with there kids.
My eldest was bottle fed because I was very young and couldn't get past many of the barriers to teenagers bf back then I was a crap mum and putting myself above my baby's needs because I only lasted 3 weeks ish with bf but dc was the only gc so nothing to compare to.
My next child born a few months after my nephew his mum had huge problems resulting in not being able to bf but when I did bf I was putting my own needs over baby's by doing it for to long and rubbing it in her face.
I learnt with her what ever I did was going to be wrong so why fret I just got a bit more confident and stopped letting it bother me fought her nonsense with facts info and disdain. It works.