Fight over moving boxes 🙄

My mom called me yesterday after I had just gotten off from a disappointing phone call. I was not in a great mood. She calls and ask if I had empty moving boxes, which I don’t because I haven’t had the time to finish unpacking, so I said no. She then goes on to tell me they’re for my brother because he needs boxes to move. I rolled my eyes and sighed because my mother is always babying my adult brother. He has money but can’t buy his own moving boxes. Instead have mommy buy them or ask people to give them to him. I have a lot of pent up resentment that’s a whole other thing so I said no I don’t have boxes empty and I made a comment that he can find them at Lowe’s or Home Depot. My mom didn’t like my remark and hung up the phone. I didn’t care. I was not in the mood. She asked my younger sister too for boxes who’s just moved out, but my sister threw hers out and apparently my sister should’ve been a psychic to know our brother was moving and keep the boxes. So she messaged us both telling us how we’re assholes and never there for our brother and she’s nothing like us because she would’ve gotten the boxes for him blah blah blah. Me and my sister got into a really bad fight where we weren’t talking to each other for a couple of months and she didn’t bother to message one of us about how we were towards each other but we don’t immediately give her precious son boxes and she waste no time messaging us. I unleashed. I told her I’m not responsible for him having moving boxes or not. That he can spend the money like I did. That I don’t remember anyone caring if I were moving and giving me boxes. I told her anytime him or his wife does anything she expects everyone to come to help but with anyone else she doesn’t bat an eyelash. She then said me and my sister don’t ask for help. I replied I did ask for help and I was moving whole pregnant. Did I get it? No. She doesn’t understand that it’s not about moving boxes it’s unsolved resentment built up that unleashes when I’ve already had a bad day and I’m being yelled at about boxes. I’m not obligated to give anything to anyone, especially two people who have money but rather spend it on other things then things they need. If I’m a asshole then I’m an asshole.