Need advice on this...

I told my parents that my son will be going vegan (he’s 3) because my partner and I are vegan. We are getting a place together soon and my mother straight up told me, “I’m not going to support that when he’s staying with me/when he’s with me”

As well as, “when he’s with me I’m going to feed him whenever I want”

Then she proceeded to talk shit about the situation to my step dad very loudly in the other room and said told me I shouldn’t be “so radical”

Opinions? She is very controlling and I think she freaks out when she thinks she has no control. I feel like if my son is vegan, he should be 100% vegan and that she should support it.

Opinions?