“I’m Living With My Married Elder Sister And This Is Happening” – What Should I Do?

Please I just really need someone to talk to about this and I will like your candid advise.

So since my older sister got married I always come to her house and spend few weeks or months and go back. Al·through my university days, whenever school is not in session I always come down here to spend time with her and her husband.
Truth be told the husband is a very nice man and has helped me always financially, anytime I come here once my sister welcomes me the first day like this, from the second day she leaves all her house chores for me, I mean everything and she just relaxes. At times I get really tired and don’t even feel like doing those chores but because most times when I come visiting she is heavy ( pregnant) so most times I just help her.
Thing is my sister doesn’t appreciate all my effort, most times she complains self its the hubby that tells her that I am hardworking and at least she should give me credit for all I do.
Now the reason why am writing this is because am done with service (NYSC) and as it is its like I have to stay in her house because the state where she stays has more job opportunities compared to where our parents live. She stays in Abuja. I have been down with malaria for few days now and I have been on treatment, just because I can’t do certain house chores because am not too strong my sis started complaining saying I can’t be living in her house and be waking up whenever i like. Mind you I was always the first that wakes up when I wasn’t sick, in fact I will wash the dishes, sweep, mop daily, cook food, bath her children and all those things.
The only thing she does is to bath her youngest baby, but now because for these few days she has been doing those work I do daily she is already saying she can’t tolerate me sleeping and not waking up on time.
My question is this, does she have the right to be so angry at me because she is doing her house chores? I feel its her house and so she doing her house chores herself shouldn’t be a problem since am not too strong to help her do it. She herself just sweep and doesn’t mop, but she expects me to sweep and mop everyday.
Should i just go back to my parents house and get a job there? Me renting my own house is not an option because am a lady and am just 22.