Welcome. Would concur with- all that has already been said, including change your names here if that in fact is your real name. Runaway bunny is the site owner/administrator.
Are you sure that ADHD is in fact your daughter's only diagnosis? Is she taking medication? Do you think it might be time for a second opinion? Would your daughter be willing to go to therapy (talk therapy?).
I would probably try a few more things, but not wait too much longer before setting up some guidelines that she would have to follow in order for her to be allowed the privlege to remain in your home.
Just saw that she is verbally abusive. This must stop.. Are there drugs involved? Is there constant chaos? These things are to be considered....and all efforts should be made to eliminate them. I would calmly tell her that being abusive to you is something you just will NOT tolerate.
If she can't get with the program...then surely eviction might very well be the solution, and sooner, rather than later.
Many of us like a book called "Boundaries," by Henry Cloud...might be something to check into. At 21, it is clearly time for you to start pulling back emotionally...time to detach.
If your daughter is discovered to have a major mental illness (not saying that is the case) and all efforts fail...you might want to inquire about social security disability for her. However, this is just something to put in the back of your head as a possibility down the road.
Would start first with a Psychiatrist (MD) for possible medical treatment and a mental health counselor or psychologist for therapy. Talk with her (your daughter) about getting a job, even a part time one, and be sure to set clear guidelines re: boundaries/appropriate behavior with-i the home.
You might also consider setting a date for her to move out...her 22 nd birthday for example, or Jan. 1st of next year...something logical to you and your family. It would probably be best for her to not stay at home and do nothing...she's not learning anything this way.
Of course, if she is rude to you and/or breaks any other house rules...then all bets are off and that move out could be changed and made asap. You might even have to look into your state's laws re: this (a formal eviction). I would offer to pay for medical services (therapist, doctor, etc.), but if she continues to be verbally abusive to you, after fair warning, I would tell her that you can pay for her to go to the doctor if she would like...but that you will not allow her to remain in your home.Then do what you have to do to make that happen.
One final thing...nurture your relationship with your spouse.
Hang in there....