AITAH for being angry at my brother for inviting over my ex-friend who treated me badly?

So basically, I (18F) is staying with my mother (55F) and my brother (21M). I’m only home about less than half the year because I’m at university, so I’m mostly here during breaks.

My brother became friends with a girl named Laura (19F) right after she and i stopped beeing friends. She used to be my friend, but we had a falling out because she caused me a lot of problems. She would lie about me, tell people very personal things I trusted her with, and constantly try to put me down, especially in front of guys. She acts completely different around men, and it really messed with how and what I share with friends now.

My brother doesn’t have many friends, so I was okay with him being friends with her as long as he didn’t invite her over when I’m home. I told him this clearly because having her in the house gives me anxiety. I can’t stop thinking that she’ll snoop around and then tell people embarrassing things about me, like she did before.

Yesterday was already tense because my mom invited my grandmother (her mom) over. I’m on very bad terms with my grandmother because she has insulted me in the past calling me a sl*t because of my body and even accusing me of trying to seduce her 70-year-old boyfriend. So I was already upset that my mom invited her over while I’m here, especially since I’m not home most of the year.

After my grandmother finally left, I wanted to go downstairs to play with my nephew. But my brother texted me telling me not to come down because Laura was over and he knew seeing her would make me upset. At that point, I completely lost it. I hadn’t eaten, I’d already been stuck upstairs because my grandmother hates me, and now I was being forced to hide in my own home because he invited the one person I asked him not to bring over.

We argued in our siblings’ group chat. I explained why Laura is a bad person and why we are not friends anymore. My brother said she never did anything to him, so he doesn’t see the problem. My other brother (35M) is also defending him.

Now I don’t know what to think. I would’ve gone back to my apartment early, but my birthday is planned for Saturday, so I can’t leave yet. I’m really angry and don’t want to talk to my brother right now.

So… did I overreact? Or am I justified in being upset and needing space from him?

TL;DR: My brother invited over an ex-friend who lied about me and shared my private life, even though I specifically asked him not to bring her over when I’m home. AITAH for being angry and not wanting to talk to him right now?