How to deal with a grandmother who is depressed but also lashes out on you?

Yes it's me again. after 3 hospital stays in a year my grandmother is yet again lashing out and not eating much for the past 2 days. I feel like I'm way over my head. I tried to get answers and I was informed that she has no dementia and that all levels are good just try to get her out of the house. Well I tried that and no avail she refuses to leave or stay in the house. She has been acting like a lost child. Ever since her best and only closest friend died when they weren't on good terms it seems like she has guilt and remorse she didn't get to express or apologize for what she did. Lately she has been emotional and she won't open up at all and when I try to get her to she won't or lash out on me. I feel that she is holding in what she feels. Even though she might say here and there that she is grateful that he left money for me but it was all in her name now. She has been spending on mostly herself and the money that was supposed to be for me has been spent a while ago now. It hurts me by how she acted and is acting about it. She once said she wishes he was alive so she can get more money from him. I told her how could she say that but she as usual brushed it off and said it was nothing. In a way I feel that she only liked him because he raised me and gave her money but since he isn't around she's retreating in. As the many years I known how she is her mood swings and meanness isn't new. But with her not eating to me shows that she is giving up on life. I tried to get her help but she refuses it. She refuses anti depressants even down to seeing a therapist of any kind. She'll make up excuses to the doctors and they will take her word over me sometimes. I just feel like I should walk away and start on myself and on my life. She's been treating me the same way she treated me when I was in high school and middle school. Getting upset that I want to just spend some alone time away from the house or even in my room. I'm constantly around her and I try to get her to talk to her friends but she won't even bother to call them. Even when I call them she will pretend that she's bored or asleep so they will leave. I just don't know what to do now. I was practicing my guitar and studying for my drivers test but every time I want to she will throw a hissy fit. At times I feel like she intentionally makes herself sick knowing that I will help her either way. She even took advantage of me by drinking mostly all of some alcoholic beverage that I wanted to save for my birthday this year. She drank both bottles that I had. When I brought it up to her she acted like I was attacking her when I simply said hey if you wanted one you could had had it but not drink both of them without asking me. She can be nice at times but mostly she can be very vindictive and mean. She hated this lady for no reason at her job she had last year. The lady asked her why do you hate me so much and she said because the way you act. She can be like a spoiled child but yet everyone is the bad guy including me. She can be an injustice collector. Yet when she gets sick she will blame the doctor or will tell them that I did it. It hurts how she's been acting but I really need some advice. She's too independent for a nursing home or retirement home and they are too expensive. I feel like I should get out on my own and just check on her on my off days if I can get a job and make sure she's eating. But I feel it's time that I let go and start on my life. I just don't know what else to do. I try to get her to accept the help i give her even when its just someone to talk to or fix things that I can't fix to getting assistance with things and she will then lash out on me about it, or say she can do it her own self. Should I just let go and just honestly stop caring so much and make sure she's okay and make plans to take the bull by the horns and start living life?