Lisalisa, first of all {hugs{}}. It's a very difficult and painful situation for you. I think Shrub has given you some excellent advice. If I may add a bit, only give your mother the minimum of information, and don't expect her to remember anything in the way that you remember it.
If, for example, you decide that you have to go out on a Sunday, you don't need to tell her exactly where - that way she can't follow you or tell you how you should be doing it.
Of course she will heap coals of fire on your head for doing that! But just let it wash over you - I know it's very hard to hear that. This is what I say to myself 'She is saying that because she has a problem. Her problem is nothing to do with me - so what she is saying is nothing to do with me.' You need to believe in yourself, practice, and eventually it really does work.
Even if you manage to have a clear discussion with her, or you lay down the new ground rules simply and succinctly, don't expect your mother to remember them as you do. She will remember things as is convenient to her.
I doubt very much whether she would succeed in getting Social Services involved, and even if she did, I doubt whether they would find anything wrong at all with your family - they would soon see the true cause! To strengthen yourself and your family, why don't you have a talk with your Rabbi? Mention your concerns and create a link with him, so that if SS were ever to investigate you, you have an active connection with a respected person to help vouch for your characters.