Anger/Hatred towards others

My grandma has breast cancer. She had a double mastectomy on August 1. After the pathology reports we found out Its stage 1 in the left breast area, stage 3 in the right. she is going to need chemo & radiation & hormone therapy. They didn't even think it had made it into cancer in the left breast, they mri/mammograms, etc. all showed pre-cancer, however, the pathologist found actual stage 1 cancer. She has a 56% chance of the cancer returning in the right, 8% on the left. Also, we found out She has 2 types of breast cancer. They can't believe it --the doctors, they said this NEVER happens. She is now a case study @ the Mayo Clinic.

She was SUPPOSED TO go this week for some scans --bone scan, heart scan, chest scan, to check if its went into her bones, heart, etc. So she drank all the contrast stuff the night before, went to the hospital yesterday and the REFUSED to let them inject her & do the scan. Last week at the appointment to remove her tubes she FREAKED on a doctor who said they may be draining to much to remove. She REFUSED to let the doctor examine her, then went to the parking lot & locked herself in the car after cussing all the doctors, my grandpa, etc.

 She has become SUPER hateful to me, my aunt & my sister, my grandpa, etc. She told me last night she is giving up. She cussed us all a blue streak, told my grandpa who cooks, cleans, etc. for her that she HATES him & he is worthless, etc. Grandma said she is tired & sick and that she is 68 years old & is tired of people telling her what to do. She is normally a difficult person anyway to be honest, but, yesterday she was SCREAMING at my grandpa that she hated him & it scared me. It was like it wasn't even her in there, it was like another person in her body. I am worried for my grandpa, he isn't eating because she isn't eating. He shakes so bad that he can hardly drink from a cup. 

I told her she needs to stop fighting all the people who are trying to help her & use that fight against this disease. I begged her to fight, I lost my mom when I was 14 & I am 30 now, so my grandma has been like my mom. I told her my mom wouldn't like that she is giving up, and what did she think my mom would have to say about that. VERY hatefully she said "well your mother isn't here & she can't say anything!"

What can I do? I have been taking turns with my aunt & sister taking her to appointments, I would go 2-3 times/day to drain her tubes when she had them, I have cooked supper, picked their garden, etc. I have 3 kids, work fulltime, and have my own husband, house, etc. to take care of. I am SO stressed! And she says I am trying to treat her like a child, and that we try to tell her what to do.  I am ready to not go around her until she changes her attitude, but, then I feel as if I am abandoning her & my grandpa. 

Is this type of behavior normal? What can I do? I don't want her to give up. Do I just have to accept this? Any help, advice, etc, is appreciated.