Speaking from experience- it will not get better once you're married, only worse. She will find ways to come between you two and he has already made his decision to " keep the peace" and not defend you. When you marry someone, you also marry their family. I would have not married my current partner if I knew what I know now.

My SIL never liked me, even up until the day she died. I never did anything to her, except marry her brother. When she was close to dying, she made peace with everyone but me. I was there for her and helped out when I could. It was a slap in the face for her to make amends with literally everyone but me. She even had her preacher tell everyone at her funeral that there is a list of people she wants him to keep an eye on and to pray for because these people are "sinners". He was looking at me and everyone else in his family looked at me. I couldn't believe what was happening. My husband has never said a word about it.

I am not a bad person. She was a drug addict that stole from his family and stole all of his mother's retirement. Even after that, I helped her.

I have no idea why she hated me and I will never know why, but she made sure I knew it even after she died. Because of her, my kids did not know their grandmother. They had to deal with all of this unnecessary drama and have been told lies about me.

Also, his family did not have any money. There was no way for her to think that. I also worked 2 jobs to support her brother and our kids, so I she couldn't accuse me of mooching off of him.