How do you know the difference?

I was told this weekend that I am “to sensitive”. That I takes things to personally. I think I am very intuitive and can tell when something is off with people. My sister lives in Mexico and up until about 6 months ago she would write me wonderful long emails. She posted a lot of interesting things on Facebook. Around the time of the election things got a little off. Months after that she sort of disappeared on me. My emails went basically unanswered or just a brief comment. I couldn’t believe it was about our differences but something was wrong. I asked her…at least twice and she said “nothing is wrong” very tensely. I sort of gave up. But yesterday, I finally found out what was wrong and it has nothing to do with me. This happens to me a lot. I think “what have I done” and frankly sometimes I have offended someone and need to say I am sorry. I know people are in charge of their own feelings but how do I know the difference between being “to sensitive and insensitive”. Hope that makes sense. I have been so upset over my sister’s lack of communication because I was sure I had said or done something to offend her.