Why does my grandmother hate my mum (her daughter in law)?

Anonymous
We are a British Indian family in England. I live with my parents, grandparents and sister. For context, my dad doesn’t speak to my grandmother because of something that happened years ago (I have no clue what). I assume it has something to do with the way my grandmother treats my mum.

Again, I have no clue what the backstory is to my grandmother hating my mum as it goes back years. All I know is I have grown up around this tension, so it’s been going on for around 22 years. I have seen my mum reduced to tears due to how my grandmother treats my mum.

The latest incident was yesterday night where everyone but my grandmother were sitting together watching TV and we could hear her in the other room swearing to herself, presumably about my mum. She came into our room for something and we could hear her muttering the same word which translates to ‘bitch’. After she walked back out the room my dad was getting quite angry that my grandmother treats my mum like this after everything we do for her. My mum being the woman she is, she doesn’t want any conflict so she always tells my dad to just leave it.

Anyway, an hour or so afterwards, my dad told me that my grandmother also said something that translates to ‘person without a father’. This hurt me so much because my mum recently lost her father due to a heart attack.

It just hurts me having all of this happening because I don’t know how I’m supposed to act with my grandmother. I hate the way she treats my mum. What do you guys think about all of this?
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Why does my grandmother hate my mum (her daughter in law)?
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