Child and domestic violence? Please help?

So I've got a very serious question here... I'm from Moscow, Russia, 15 years of age, and here's the deal: I once lived in Georgia (Tbilisi) as a child (from 5-13 years). My mother (russian) left my father when I was about 3 years old and took me (and my older sister) to her side. She hasn't graduated from a university at her time (in-fact, she didn't even go to the last, foolishly saying that she wouldn't need that) and never had a job. She always had new wealthy and old boyfriends (although never for too long, we... I always lived in a 1-room appartment - she was always out either at her boyfriends' house or partying or whatever), there was never really any food in the fridge, although she sometimes took me to some parties, stating that I must've eaten a lot, for I that should be enough for some days to come. She always used to beat me till I bleeding with either a stick, a TV cable or a horse lash. She used to throw her mobile phone and other things at me if she liked to (and I was standing out of her reach). She also always humiliated me, using curse words, and almost molested me (making sex jokes about me and e.t.c.). I started uprising to her words and actions at age 12-13 and by the summer when I was 13, she said that she'd send me to a military camp somewhere in the mountains (oh you know, where they beat kids to death) to teach me a lesson or even send me to prison of sorts, saying that she had "so many connections, everyone could f**k me around". When I was about 8 years old, she got around with a criminal - yes, a criminal - who was in jail more times than I can count. Eventually (13 years), then my grandmother arrived (from Moscow), to check on us and she saw the situation, although my mother was trying to hide it in every possible way, saying that she'll kill me if I spill something out. Still, my grandmother made my mother a proposition: what about sending him (me) to a military school in Russia? Of course this was a trick, and my mother sent me with my grandmother away to Russia. When we arrived to Moscow (my birthplace), it seemed like I finally broke out to my freedom... until my sister came to Moscow. She said that she was under a lot of pressure from our mother and e.t.c. However, my sister had a "character" and she tended to get really angry. At the new year (on my 15th year of age), she decided to leave to our mother, which seemed to move to Turkey, since her criminal boyfriend (now husband) was wanted in their old country. She came back hating us (me and my grandmother) and seemingly "loving" her mother (seemed quite brainwashed to me, she was told that she'd get to live really good at her mother's side, while mother didn't, nor her new husband, have an actual job and were living for who knows who's money). And so, our mother got a step in our home in Moscow. Those past 2 years I felt free to live normally. Of course now I'm physically more than capable to stop any threats of physical violence, lethally, if necessary. Now, this summer, she came here saying that she wants to take me to Turkey (to her new husband), and if I don'y comply, she'll take me by force, stating that she could contact the police (since she was my mother and she could do whatever she wanted to do with my till I was 18) and they'd take me into the plane by force. My question is: is she bluffing (because I think that if she's going to throw law in all of this, I can go to the court or whatever and say how she treated me when I was a child and that she wants to take me to some criminal, that is also wanted), or if she can actually do that - what should I do and how do I stop it and free myself from her?