Having issues with my bfs mom

She hasnt liked me since me and my bf went through a rough patch and broke up. We have been together for a year now. We started college in august and are long distance. His parents have a restaurant where he works. I am happy that he works and has a good income while he takes classes. But when i come home for a weekend he takes off to see me. Every single time his mom gets mad at him for something stupid and makes him work when he was supposed to be off. It sucks because i want to be with him and she does it so i can't be with him. I get upset at him but don't want to strain his mom and his relationship. We have talked about it nad hes 19 and lives with them. What can i do to compromise? Its just that it annoys me