Daughter is 18, does parent have rights

My daughter is 18. We live in Illinois. She has a boyfriend. She has been in and out of counseling for depression for the last year. She went to a "counselor" that was picked by her boyfriend's family and the boyfriend sat in the room during the sessions. Today, the boyfriend and his family took her to a hospital in St. Louis, MO and she was admitted for observation. I believe the boyfriend is part of her problem. I have notes written from him that state he will kill himself if she ever leaves him. When I tried to see her and stop her from going with him, she had to ask him for permission to see me. I want her to get the treatment she needs. Do I have any rights as her parent? I just want him to leave her alone at least for a little while so she can get treated properly. What can I do?

Legally it is more difficult now that she is 18.

Your best option may be to keep persistently but gently trying to communicate.

If there are issues of harm or danger, you could ask social services or the courts to intervene even without her permission or consent.