Wanting to cut all family ties. *long*

My mother had me at 15 (not dissing anyone who was a teen mom) but my mom had absolutely NO idea how to raise me so she didnt... my grandma did until I was about 6 or 7.. the man she was married to until I was 14, beat the shit out of me and verbally put me down 24/7. I was thrown out of the house at 15, graduated at 16 and was off to college afterwards. My mom hadn't talked to me since I was thrown out at 15 until she found out I was pregnant with my daughter at 20.. since then she has kept scarce contact with me just on Facebook to keep in contact with my daughter.

My in laws are literally my heart. They are the best people I could ever ask for and will be there no matter what. They feel like my mom is just the scum of the earth for how she has treated me.

Recently my half sister graduated. Everyone threw her a huge party and even bought her a new car and her own apartment.. of course I'm extremely hurt over it and it's got me thinking. I want to cut all contact with everyone... except my grandma..

The only problem with that is my mom and my grandma live in the same duplex... so I feel like everything I will tell my grandma will be relayed back to my piece of shit mom..

Has anyone else ever gone through this or have any ideas on the best way to go about It? When I try talking to my mom it just blows up into a huge fight..

Should mention my entire family and I are on complete opposite ends of the US from each other thank god so that would make it easier to just disappear from them..

Thanks for letting me rant haha.