Feeling horrible

I can finally see that my dd needs mental help. How did I miss this as she was growing up, or is it something that just happened suddenly because of stressors in her life? She is 19 now, so she has to be the one to call a therapist and make an appointment. Unless she tries to harm herself there is nothing we can do. I don't know if it a specific situation, but she has had 2 very pshchotic episodes, the latest was Saturday morning. She ran from the house with nothing, not even shoes. I finally found her about 2 hours later, laying on a lawn crying, with blisters on her feet. I convinced her to come home where she cried and screamed for well over an hour before I finally went in and refused to leave her, even though she was saying she hated me, her life and everything in it. I fianlly just grabbed her and held her and cried with her. This calmed her down. I put her in the tub, gave her a sleeping pill and layed with her until she fell asleep. Everytime she woke up for the next few hours she cried for me to come and not leave her alone. The scariest thing is that she doesn't remember most of what happened. I know the trigger was her ex, but not why she went so crazy. We are going to tell her that she HAS to see someone. She can keep trying people until she finds someone she can talk to, I will got with her, or she can go alone. But, she has to go. I try looking back at her life. She has always been stubborn, from the very first day she was born. She is so different from my other 3, but I never even considered that she had a mental illness. How do you identify it? She did great in school, but she always did have trouble keeping friends, should that have been a clue? I wish I had known, I wish I had paid more attention.