Hello, first time posting here. I have an aunt, Kay, who estranged herself out of our family. For stupid reasons that I can't understand. Here are some examples of the things she does:
1. My mom was pregnant with me and Kay and her husband were visiting. Suddenly she gives my mom the silent treatment and completely ignores her to the point where my mom is crying. She didn't talk to my mom again until 3 years after the fact. Why? Because she saw my mom spraying on hairspray and hairspray is really bad for the ozone. 3. Fucking. Years.
2. About 12 years ago my grandmother (at that point my grandma is the only person from our family who Kay would even talk to. They are on the phone and my nana mentions that she got a new car. Kay was like "What? Why didn't you ask me if you could get a new car?!" And then my nana says, "Honey you don't have to ask me if I can get a new car. that's my business." So of course after that Kay stopped talking to her for the rest of my nana's life. She didn't even come to her funeral. 

Please if anyone knows what this could be please tell me. I have a lot of anger toward her for obvious reasons. But I would love to know if she has some kind of illness so I can stop being angry at HER and try to understand her mind and forgive her.

tl;dr aunt does some crazy stuff. Curious about her mental disorder.