Why should you ask for forgiveness from your sister? What are you guilty of?

Don't worry so much about who thinks what of whom. What goes on inside of other people's minds is their problem. I was in a psych program where they had a sign on the wall that said, "What other people think of you is none of your business." I had to ponder that for awhile. Then I started to see the light. Stop reading other people's minds, even if you're good at it. Deal with behaviors, not with the turmoil inside of other people's heads.

Right now your husband and your sister are avoiding each other. That's okay. Take a step back, and don't be in the middle of that. Your mom promotes a lot of this bickering. When your mom tells you to apologize to big sister, just say, "I'll think about it." Say it with warmth and sincerity. Then change the subject and don't spend 2 minutes thinking about it. If Mom brings it up again in 2 weeks, just say gently, "I'm still thinking about it." Then forget all about it. I think this family of yours has been playing with your head for a long time. It's time to flip the script.