You can not give up on somebody. That implies that you have control over another person, and you dont. You are simply taking your life back, letting your oldest have a chance to realize she needs help, and saving your youngest, who does not need chronic drama in her home.
Your daughter will carve her own lifes path. Right now she isnt very stable, mature, or safe. You said she gets violent. Your youngest doesnt need that nor do you. Her mental health is in her hands now. She is eighteen and you cant force her to realize she needs help. She has a better chance of realizing it if nobody rescues her.
I hope you feel better about it soon. Think of yourself and your younger one...
