I stood up to her, yet she grounded me even more, she is a close minded "mother". Why do people think I just went, "Please unground me..." I DIDN'T
Alright then, I reiterate my other statement then:
"Your frustration is, of course, reasonable, but you will have to realise sooner or later that this is just a common bump when you have younger siblings. Especially when that sibling is 4. Your mother will eventually come around, dear, and things won't be as tense in these quibbles. But your better off trying to eventually become friends with your sister than start off early with an excuse not to get along with her."
And, as for more directly towards your mother's actions: Parents can be unfair sometimes. People can be unfair sometimes. But their humans and as much as we may think they should be perfect in their actions because of their title and or being, they aren't. That's why the "Grand" part isn't added until later.
Do what you will, though. Maybe it would be good to tell here just what you feel; Both of you must grow, together. She has been your parent just as long as you her child. How else can you two learn but by experience? Hm. Good luck, in any case. c: