AITAH for always telling my sister no?

I‘m not going to specify my age on here but I’m a teenager girl with a younger sister. Me and her don’t have a huge age gap, but it’s enough to where we have different interest. That being said she often asks me to watch movies with her or play with her, which I wouldn’t mind that much if she didn’t make it such an issue sometimes. My social battery is strange so sometimes I’ll be really talkative and loud, and other times I want to be quiet and alone. My sister fails to understand the second one though. If I play with her and then tell her I want time to myself, she’ll beg me to keep playing. She also is very invasive at time, like she’ll come into my room for no reason and when I ask her to leave she just keeps talking as if I didn’t tell her multiple times to get out, or when I’m on the phone she keeps trying to add herself to the conversation or say hi to my friends 1000 times. My biggest issue is she can’t accept the word no from me. If she asks to be in my room or borrow my stuff and I tell her no, she begs and begs and either gets mad or starts crying when I don’t change my mind. My parents and I have spoken to her multiple times about this but she keeps doing it. I always feel bad afterwards because I feel like I’m being unnecessarily mean, but at the same time I feel like she should just respect my boundaries. She’s old enough to know what no means, and when I do say yes I almost always regret it. I let her borrow something? Now she feels entitled to my stuff which she often breaks, loses, and/or doesn’t ret unless I ask for it. I let her eat the snacks I buy with MY money, now it’s suddenly her snacks too. I don’t want to be those old siblings who treat their younger siblings like shit and then try to act like the victim when they get older, but it’s annoying to me that she cries and gets upset every time she doesn’t get her way. I literally don’t know what to do anymore.

Am I the asshole?