Please someone help me; she's lazy;treats me like a housemaid; she never washes or showers; you no when she has entered the room just from the smell; always picking on her sister who's 9; I'm crying while writing this; how do I ask her to leave; can't take no more

Where do you live... as in country and state.

Many places consider a person to be an adult at 18 and thus legally responsible for supporting themselves.

If you are in such a location... you lay the law down to her. And you specify what you expect of her if she is to continue to live under your roof. DO it in writing... make her sign it. Its not a legal document but she can't argue you never told her as she will likely try. Its not open to negotiation... Its your house.. its your rules.

If she refuses or fails to do them all, you tell her she will have to move out... if she thinks you are kidding... file to have her evicted.

Sometimes it takes tough love to get an irresponsible child to grow up and act their age.