My brothers fiance doesn't treat him right. What should he do?

His fiance gives out to him if he is out having a drink with his friends, if he is late to meet her and if he messes around having a laugh.

She can be very bossy and gives out if he does something wrong. He always defends her if i say something.

I met them for lunch one day and she wouldn't come to the house to pick me up. When i said to my brother about me getting home cause i have a bad back, he says to me don't say anything about it in front of her. That he didn't want an argument with her.

Updates
+1 y
He was invited to her brothers wedding where she is bridesmaid. He became sick a few days before the wedding. He told her he might not be going cause he's sick. She got mad and said how much her brother spent on the food and that she came to our uncles wedding when she was sick. She was able to walk about, my brother was sick in bed. She eventually became worried whdn she heard how sick he was.
My brothers fiance doesn't treat him right. What should he do?
Post Opinion