I am not a parent so you can take this for what it's worth. Recently I've spoken to friends who have older kids and are going through similar situations, myself included, as I am the step parents to an 18 year old and a 16 year old.
Our 18 year old is almost EXACTLY like your 20 year old DD.
Creating a sense of entitlement with your kids often starts YEARS younger, when they are young. It is extended through their teens and young adult hood. Then suddenly, a parent changes THEIR expectations and the child is left shocked, scared, hurt. They take the defensive, rebellious, 'fine, I can and will take care of myself' often not even understanding the full breadth of what it takes to take care of themselves.
Our 18 year old is a prime example of this. My husband felt guilty for wanting a divorce. He tried to make it up to the kids by doing EVERYTHING for them, not teaching them how to do chores, making sure they were never sad, disappointed, hurt, etc... He spent $$ he did not have on their wants, not just their needs.
Then when the 18 year old turned 16, husband suddenly wanted him to ... WORK! Oh-my-gosh. Then husband bought a car for him to use, but made him pay his own insurance. Well the kid who never had to do anything his whole life suddenly HATED his dad. You'd think he'd be happy that his dad bought a car for him to use, but NO, his Dad just gave him a responsibility and no choice but to take it and pay the bill. He didn't like growing up ONE bit! So he became rebellious, thinking that all it took in life to be able to pay your bills. OK, so he can pay his insurance, he must be able to take care of himself right? uuummm.... nope, obviously not. Vicious circle... more mad at us because we throw responsibility on him because he is old enough, but is he mature enough? not really... but how else do you make kids mature?
Honestly someone said to push them out of the nest.... thats probably what needs to happen... they will be mad and they will push you away.... but they come back around as more normal people around the age of 22! haha Remember when you were their age, the influences, the scary world, the hormones, the trial & errors. It is how they grow, learn, teach themselves, realize that you are not the enemy.... then they come back.
Just stop enabling them.... you can't buy them back and you can't win their love. You need them to respect you, respect what you've done for them and love you for all you continue to do for them and always will do. Being a parent is such a thankless job until they are 100% on their own and live as good solid people! Then you get to sit back, look at them and thank the lord.
(((HUGS))) to you!