Arguing with the past

I was not accepted into my second marriage family. The SILs were pretty cruel and even admitted to being so but basically did not like me nor the fact the I married their brother. I wrote a letter to one SIL which was quite pointed and uncensored. At the time I felt it was a good idea. I now know that I should have babysat my brain. There has been unresolved feelings for years and no closure. Now that I know that it was my thinking do I open up the can of worms and contact SIL? Do I rewrite the past for me? I feel compassion for me. I love me through all of it but it still has consequences for today. Can a relationship be healed when nothing has been talked about for years and people’s opinions are set in stone and I know I have no way of changing them?

My one on one work coach said that I can’t change the past but how do you move towards building this relationship now? Does this require a sorry email since I do feel really badly? How do you right the wrongs of the past with others? I have done the work to love myself through it but how does one approach others when time has passed?