I did not know that the Jewish religion was against divorce. You sign yourself as a Christian. Are you proposing that if you attend this wedding you are condoning divorce?
I am a Catholic, but I think that the most Christian thing to do would be to attend your sister’s wedding. You are family, after all.
You do not know why she divorced. As far as I know, divorce is not a scandal in HER religion. As a Christian, it would be better for you to attend and keep the lines of communication open between you, unless there was a public scandal involved in her divorce that was known to be her fault.
It's not. We invented the pre-nup.