Right now, I'm living with my family in a 2 bedroom apartment [meaning I have to share a room with my mom - I am 18.] She's been in a wheelchair for the better half of my life for balance-related issues, and it seems the closer I get to being able to leave and start a completely new life the harder the holds on. I'm like 100% sure this is normal with most parents, but she has never had me on anything but a ridiculously short leash. I sleep in a bed that is directly pushed up next to her, I leave the house to go to school and come back home and any time I attempt to go out with friends I either have to cancel or I come home to her being furious that I left her.I can't make any commitments and miss class a lot because of this.
Her health problems have been getting worse lately and she's been in bed almost constantly for the past year, though doctors tell her if she goes outside she WILL get better - she refuses and says she is too weak. On top of this, her mental state is getting really horrible as well. As someone who suffers from my own problems, I'm finding it hard to deal with this and the things she says to me are getting to me. Nothing I do to help satisfies her and I get old that I have a horrible attitude and am such a cruel person to let her live in filth [untrue].
I happened to go out with a friend a few days ago and then, at 2am, I get like 10 phone calls from her saying she received a blank text and that I was killing her and that she wanted to call the police to see what was going on. These types of things happen almost daily in addition to her "You have no idea how bad I feel, it wouldn't kill you if you cleaned but, whatever, I won't live much longer anyway. Enjoy your night" text messages.

The way we live is ridiculous and yet I still love her a lot. I may be able to leave for college in a few months and my dream school is a few hours away. I have no idea how to let her know what, if I get in, I want/need to leave and start a life where I am not tethered to her completely. This move needs to be a new and positive start for the both of us but any discussions about this end up in her twisting me into some sort of sick monster for wanting to leave her alone and "condemning her to die" because I won't be here. My whole life, she's turned my family into an us vs them type of thing against my father and her mother, meaning I've never gotten close to either of them, but now it's been a her against the rest of us type of thing. In her mind, all of us want her dead and it is delusional.

She refuses all help or attempts from me to get her to a doctor [both for her health and mind], and she doesn't really follow any instructions from doctors because she goes on google all the time to search and diagnose her symptoms. While on her computer, I found a few sites "favorited" by her that were for coffins, how to handle emotional abuse and planning funerals.

Honestly, it's getting to the point where I'm just frightened and completely worried about her doing something extreme, since her moods and words are getting so harsh and insane. I don't know how/if I should leave and bring up the subject with her that will turn it into something good. I want to live, but not like this. How could I go about doing this and getting her the help she needs?