Mom issues

So my mom tends to tell everything to my older brother, who in fact is in Mexico right now. Well what she feels like telling him. My bf and i live with my parents to help them out financially. So a month ago we had an argument and he decided to leave for a week so he can think things straight and i agreed to it. My bf did come back, so everything is fine, thank god. Well my mom decides to tell my brother that he left bc he didnt want to be responsible of our baby thats on the way. Mind you my bf has 4 kids from a previous relationship and he is 100% responsible with them. So like 2 weeks ago i was taking care of my nephew, he is 6 yr old and he literally said he hated me and kicked me right on my pelvis mind you im 30 weeks pregnant... Well its gets me mad bc she hasnt even mentioned it to my brother or my nephew's mom what their kid did nor has she got him in trouble. Well now my brother wants to come and talk to my bf... I told him instead of worrying about my problems come and educate your kid. Why in the world did she not tell him about my nephew but tell him my personal relationship problems?