My niece who live with me is 18 years old. Her mother pass away when she was 9. She didn't graduate to high school, she is very aggressive,disrespectful with us( my mother and me), she dosesnt want to work, either help at home, sleep until 4 o 5 pm. Only pass all the time in the computer, what we can do? She also refuse any psicological help, counselor, we live in ca. We need urgent help.

Time for some serious TOUGH LOVE here.
Lay down the rules of the house.
If she refuses to contribute, then with draw things from her, starting with computer access.

Give her a set time frame, 30 days to 60 days,

She is start helping around house at once, and start looking for job. If she does not, evict her and send her packing