Bad mom?!

So I babysit for a lady she's a stay at home mom and her husband gets off work at 12. Her son is sick and I told her I had to do my sugar test so I couldn't watch him. She goes on to say okay she understands considering I've told her before I can't watch her kid when he's sick, she always still brings him and just doesn't tell me his sick. So I do my sugar test and I failed so I had to do my second one and I told her. She said okay and that it. I could tell she was getting mad. Then the next day after that I got strep throat so I couldn't watch him again ( I did go to the doctor and was told it's what I had, I didn't just assume). She then goes on to say if I don't want to watch her kid to tell her. That if I can't watch her kid full time that how will I ever watch my own? That I'm going to be a horrible mother. I got very confused because she doesn't even watch her own kid full time when she does nothing with her days (she told me herself she does nothing). She also used me a lot in the past and wouldn't give me an exact amount of hours she was basing my pay off of. She wanted me to watch him everyday 6:30am to 3:30 then on Fridays 6:00am to 6:30pm. Non of those things were excuses and I offered my sisters help to watch him (with her permission of course) she would always say no it's fine. Her son is 6 months and I've watched him since 3 months.