Spanking grandma?

I have a four month old and am far from dealing with this issue, but my husband and I have decided that spanking will not be a go to. We don’t know what we will do in each moment because we haven’t been there and will take it a step at a time, but it is not going to be a norm. That being said, my mother seems to take it upon herself to parent my siblings kids. She will spank if she feels like spanking. Typically only if parents are not around. This makes me untrusting of leaving my child with her once my child is older. She has even spanked my sibling’s youngest before even a year old. No matter what we decide, I DO NOT want my mother spanking my child. I want that to be me or my husband ONLY. My mother had a tendency to spank for everything when I was a kid. It got so bad that she would overact, spank, and then come apologize to me for spanking. I would get so confused. Was she spanking out of anger or for a real reason? Due to this, I do not want her ever thinking she can do that to my child. What are your thoughts? Is this a situation where I can say no and she will listen or what? She seems to think she is the only one who disciplines my siblings kids and takes it upon herself to teach them “correctly.”