Family problems??? Help!!!! Sorry kinda long?

Well my brother has a girlfriend named Kamie. My mom isnt that fond of her and i am getting stressed. Here's the story: Today my brother asked my dad to bring some of his perscription to Kamies house. Well We were going to look at some tires so we thought we woudl take it to them than. My mom doesnt have a job and so she said why are you bringing this? My dad said because Derek (My bro) Is goign to let Kamie have it. My mom starts to flip out kind of because she doesnt ahev any money and she says that she cant take responsibility for Kamie. Shes nto out family and we dont need to take care of her. Well Derek has to do pretty much everything for Kamie. He Has to take her home from her friends house ect. Well he doesnt ahev to but he chooses to and he doenst ahev a job or a car. Hes 19 and he doesnt even go applie for jobs so he cant get a car. What my mom is pissed about is because he uses her car, Wich is kinda expensive, and he asks for it 24/7. My mom doesnt want to keep giving him gas money to go to kamies house and back every single Freaking Day!! Well tongiht my brother came into my moms room and he started yelling at her saying " You dont even like Kamie! She doesnt even feel comfortabel to come over,thats why we go to her house evryday. I cant remember the whole consvo but At the end my dad came in and asked what was the problem and my brother said your wifes a Bi***,Thats the problem. Then he slamed the door and my mom started to cry and than my mom Got up out of bed and got a bag and started packign everythign. I asked her what she was doing and she said she was leaving. I asked why and she said i cant stand this anymore. She started to pack everything and i went to look o rmy dad and said moms leaving. Dad walked into the room and asked my mom what she was doing. She said im leaving i cant take this anymore. My dad said this kinda loud but he said you arnt goign anywhere. Derek left. Hes goign somewhere and you arnt. Than my mom started to cry even more and than she put her clothes back and all of her make up stuff is in the bag still. Im afraid that in the night shes going to pack everythign up again and leave. She said i could come with Her. I really dont want to leave. I asked her if she was going to come back. She said i dont know. I just need help! My mom goes to a support group and everything. I am just so stressed i feel like running away for a day or 2. I hate this! I dont know what i should do. Please help i want to cry right nwo but i dont wnat to make a scene.