Hi FeelingConcerned,
I'm not a parent, but I can understand why you're concerned about your daughter. You may be right that she is not taking meds or going to therapy and possibly engaging in other harmful behaviors. I can't imagine how scary and frustrating this must be.
I do think you have done all you can do in this situation. She is an adult now and has to take responsibility for herself. You can be there for her if and when she asks for help.
I think Nowinners had a good idea about support. Have you heard of the National Alliance for Mental Illness (NAMI)? They have free support groups for people with mental illnesses and their families. It might help you to meet other parents of mentally ill people, so you can talk to them about it. I attend a support group for mentally ill people and have found a great deal of comfort from talking to people who understand what I'm going through.
This is a very tough situation though, and I'm sorry you're going through it. I hope your daughter will be ok.