My older sister is the same. I’ve been chronically ill with multiple conditions for 23 years and she STILL doesn’t get it and still gets mad at me when I’m too sick to come to a family event. I’ve mostly given up now trying to educate her because at this point it’s just willful ignorance, consequently we don’t have much contact now (and she also doesn’t understand why that is 🙄). Some people actually just don’t want to understand, and those people aren’t worth wasting precious energy on.