Is there a medical reason an elderly person could become extremely petulant and stubborn?

As my mother ages, she is pushing more and more people away because she gets angry at everyone, takes offense at the slightest perceived slight, and things have to be 100% her way. She doesn't have dementia in as far as her mind seems fine. She just requires everyone conform to what she wants. If you don't, you get ignored for weeks or months at a time. She won't call, or accept your call. But if you call her bluff, nothing is wrong. I love my mom, but I really don't know how to handle her and keep her part of the larger family group when she is constantly upsetting them. I live 5 hours away. She has a full life where she is and is not ready to leave it. She has an active social life, a wonderful circle of friends, and there is some family that live closer than I do that she visits regularly to see her grand kids. She has an open invitation to move in with me at any time she feels she needs to but I don't see her leaving her life where she is and I would never force her to. But how do I handle the petulance and anger? And could this be caused from something medical?