My grandma gets mad at everything!

Hi! So my grandma gets mad at everything. This past Wednesday she was supposed to go to North Carolina to see our cousin graduate! She reserves a ticket and our cousin tells her and her and her husband have plans after her graduation and that she can go stay with her mom, then she will come back and pick up my grandma after the plans with her husband of course. My grandma goes off, and tells our cousin that “Oh she’ll just stay home and not go to the graduation anymore since she things she’s not welcome” our cousin explains to my grandma that she is welcome , but our cousin would pick her up after he plans. My grandma then goes and cancels her ticket and shuts our cousin out and says she’ll just stay home. And that she doesn’t want to go anymore? Why does my grandma get so mad like that? She does the same thing to me, just shuts Me out and doesn’t talk to me. She did that when my aunt asked me if I wanted to go to Paris , France with her and then of course my grandma wanted to go and I talked to my dad and he said him and My grandma couldn’t stay together, grandma then got mad and started talking about how “African people are weird” and all this stuff! When she gets mad, she also starts talking about my biological mom. Im moving in with my boyfriend in 4 months. Im so done living here. My grandma gets mad because she can’t get her way but then always says I have an attitude. Oh yeah and when I was leaving to go to school the morning our cousin left our house , she was outside walking our dog and asked me did she leave ? And I said yes and then after that she whispered “yes” under her breath like she was happy about it or something. What should I do?