Is this abuse or just 'tradition'?

Every time I visit my husband’s family, I end up cooking, cleaning, serving everyone. His sister-in-law just hands me her baby and says 'You know how it is, being the younger bahu'. But I’m not even that young! I have a job too, you know. His mom expects tea ready by 7am if I’m there, and if I don’t do it, they make comments like 'city girls have no discipline'. Last week I finally said no. Just sat and read my book while they all ate. My husband didn’t say anything, but his brother laughed and said 'She herself thinks she’s a guest itself'. Later, he told me 'You hurt Ma’s feelings. It’s not that hard, just be nice'. I feel invisible. Like my work doesn’t count unless it’s unpaid and in their house. I love my husband but this… it drains me. Actually, I don’t even know if love is enough when you’re treated like help. Is this normal? Is there a line here that’s already crossed?