Sister not speaking to me

While I know that a persons thinking causes their feelings, most people do not. My sister is not speaking to me because of something I said to her. What I said, in my opinion was quite benign. I guess she doesn’t think so. I have all ready told her I was sorry. That I am sorry if I said anything to offend her. What more can I do? How do we deal with people who believe that the way they feel is caused by “us” rather than their thoughts? I know she is “allowed” to feel anyway she wants, but she is blaming me and it feels bad. Advice?