i know your situation. it sucks ass having to rely on other people for help. but the fact of the matter is, it sounds like you really do need your mom's help right now, so personally i don't think moving out is the greatest of ideas, however tempting it might sound.

communication is key when dealing with other people and easing tension. your mom isn't solving anything by locking herself in her room. and, at the same time, i don't think telling your sister off is solving much either. in my opinion you should really consider getting your mother and your sister together and having a quiet, nonviolent, cooperative conversation about any current affairs. violence, screaming, and being the loudest person in the room isn't the proper way to get others to see through your perspective. you're going through a lot right now, you just became an adult only 3 years ago, you have some serious health issues, and you're in a financial runt. these are things that you need to calmly explain to your family so that way they can realize what you are going through.

considering the fact that your mother wanted to be with you at the doctor's office, and the fact that your sister was attempting to back you up (even if it was for the wrong reasons) sort of tells me that they both care about you. i don't know the whole situation, and i really don't know the extent to which they care about you, but it sounds like they care at least a little bit. try to remember this and make sure not to look at them as if they hate you. i know your mom threatened to leave you, but i'm willing to bet that was just something she blurted out in the heat of the moment.

once again, communication is key. if all three of you aren't properly and calmly expressing what you feel and what you want, then you guys aren't ever going to get anywhere and the fights are never going to end.

and, in the end, if you give your all and try your best to calmly assess any situations and make things better, and the two still are refusing to cooperate, then remember that you are in charge of your own life and they shouldn't be drivers of it. do not let their irrational behaviors make you feel any less about yourself or what you're going through.

things will get better! i promise, if everyone just calms down and acts as rational as possible then you three are going to be able to reach some comprimises that will make you all feel more comfortable. also, i hope you get better. i'm assuming what you have are swollen lymph nodes? my uncle had those a while back but he made a good recovery and he's all better now. just keep your chin up and look forward to a better tommorow instead of dreading a shitty one.