Whose fault is it when you unintentionally hurt someone?

Well, I unintentionally hurt my stepgrandma, only to find out later, because she never came to me about me, and I've been thinking of reaching out to her to make up, but a few days ago she slipped into a coma and the doctor said she's not going to make it. Was it my fault that I didn't make up to her sooner? Whenever I saw her in family gathers, she always had this unfriendly face on, so I never approached her. And now it is too late.