ADVICE please please please

So mum has 3 month old twins. With her boyfriend whom very much doesn't like me and I don't like him. He doesn't live here but she's moving away 40 minutes to another town so my sister can go to a school and to be closer to him. But my schools here. 
I have the option to move in with a friend and pay board and have my own studio out the back to myself. And can get to school. 
I talked to mum. She's not happy and doesn't understand at all. She's trying everything "you get homesick" (I haven't in years) "you're mentally unstable" (because I have to deal with him). 
I'm still not over my mums divorce of my dad... I know I sound selfish but what do you think? 
I'm just so depressed here and it's not nice. And I want to go to year 11 and 12 at school. BUT if I don't move out soon then I'll be going to tafe so I can get a job in July and move out then. (I'll be 18 then). But if I move in with my friend I can stay until I'm done year 11 and 12! 
It just makes more sense to me... 
I've known my friend for years and I trust him with my life he's like my second dad and has had other teens live with him. I'm also close with his kids we get along well. My mum is also friends with him and trusts him. 
Advice? Opinions? 
I don't want to hurt her. But I feel like I need to do this. I wouldn't do it yet though I'd give it until after Christmas etc but I dunno. 
What do you think ladies?