It is hard, but having raised four boys who are in their 30's now and as a single father for their last years in high school, it is hard, if you try to control too much, it can ruin a relationship, they will end up blaming you for things when it goes bad and can destroy it. They could break contract for years ( I know) and then only hopefully they will start getting back with you latter.

At times it is hard, I did a "illegal" eviction on my 18 year old when there was drugs being bought into the home, he would not work and follow any rules. He slept in his car for weeks but figured that he had to work if he was going to eat.

She is at the age where she does need to start making her own decisions, even if they are bad ones. So she can mature and learn to make better decisions later on in life. If you do not like her decisions then she needs to move out. Plain and simple. ----or at least until she can learn to rationalize with you on a mature basis. So you can find a common grounds.
I know you love her and want her to prosper and not make mistakes and have a good and happy life. But an immature mind must learn from their own experiences... usually learning from another's wisdom does not happen much in most cases... especially from this generation.
As for her getting mad at you for your disapproval... I can identify with this. To this day when my mother does not approve of something that I do it hurts a little. Because you are mom. She lashes out in anger because she is hurt. But the part of being an adult means making your own decisions--and hoping they are the right ones-because sometimes mom (or whoever) is not always right. We are not perfect. It will be OK. You are doing fine. :-)

I see that you love your daughter a lot and what's best for her. You did the right thing by telling her your concern and don't want to see her get hurt by this boyfriend. She is still trying to find herself through this relationship and is torn between having her mother in her life and her independence. I have a soon to be 18 year old who has done similar things and blames me for everything as well but I think if you let her know that you will no longer accept her doing this, she will be forced to stop and you'll get your control back. I feel for you and I hope she will learn to respect you. I am waiting for mine to do the same until then I have set my boundaries with her. You are still her mother and will give her advice as a mother should. Even though they act like they don't want the advice, they actually do.