Moving out.

My younger brother who is an adult, just moved out of the house. My mom gets angry when he doesn't talk to her every day or reply to her text messages. He works full time. 
I'm moving out as well and I have a feeling she will be even worse with me. I'm 21 years old and I have a 5 month old. How can I get her to back off? She is a narsassist and gets angry very easily and has a problem with lying.