NEED HELPPP

So i lived with my boyfriend and his sister for a year and in that year my boyfriends sister was just very picky about things she always had something to say to me but never held herself to the same standards like if i left something out she would be upset but if she did it it was fine and recently we moved into his grandmas house and she said she was going to also and she’s just been doing it again like i put my babies diaper in the trash not paying attention and she was like i don’t want you putting trash in the garage whrn it’s already full and i was like okay i didn’t mean to i wasn’t paying attention so i will fix it from now on and then she was saying how i’m oblivious and how a peice of my hair fell out and got wet and now the sink is stained and i was just so mad i was like you only ever pick on me but never my boyfriend (her brother) and she was like well that between me and my brother but whenever it’s something i do she doesn’t care who’s around she will do it right infront of everyone like it’s just so frustrating to the point where i’m scared to even do anything in the house anymore and i’m stressing myself out so much because i’m always making sure i’m not doing something that’s gonna bother her like the other day i ran outside to grab something and she was like let’s not leave the door open and then 5 minutes later she left it open like it’s so infuriating and now i’ve started obsessively thinking about what to say if she confronts me about something new or what i could have said and i just keep doing it and i’m so stressed out i have a 8 month old who is getting into everything and just doesn’t want to be held at all and i’m just so so stressed out i’ve tried telling my boyfriend and he says to just ignore her but i’m going crazy because my body is always in fight or flight i don’t know what to do