How do you deal with mood swings and angry insults from someone who use to be so loving and kind?

My mom got sick with a viral brain injury 2 years ago. She went from being 100 percent healthy and supportive, loving of everyone to not knowing who we were in a matter of HOURS. All of her memory was wiped clean, people, places, she had to learn how to use a phone, remote control, washing machine all over again. Her memory slowly has returned to where she knows us but it's so spotty and she has little to no short term memory. It all happened so quickly, there was no time to adjust it felt like having my heart pulled out through my chest. The neurological injury affected the temporal lobe most of all and it has affected her moods, some days it's so hard being around my mom because she says mean insulting things, out of the blue and unprovoked. I feel like it's sucking the life out of me because I miss my mom, I miss her friendship.I should be use to it but when I'm in need of cheering up or good advice there is a part of my heart and head that so wants to lean on her but I can't and a lot of times I get the opposite of support, I get told off. We do have good days and I try to give thanks for them and hold onto that feeling. Our situation is made worse by the fact that I also have a severely mentally ill father, my mother cared for him all the time and saw him through his multiple breakdowns, now they both have diseases that have affected their minds, they sort of move along at their house, independent but fragile, I check in every other day with groceries, meds and just to see how things are. I get calls most often when things are going bad, mom had seizures, dad began having an episode of psychosis, I feel shell shocked and disoriented some days, who wants to put out fires on a nonstop basis? I miss getting calls with a cheery voice saying "Hey, How are you?" I have siblings and they don't help and all have their excuses. How do you cope? I feel lost and sad. Any advice would be appreciated.