We have the push-pull of her emotional state along with a huge defiant streak and extreme suicidality. Just yesterday she wanted her phone back (consequences from the day before) and I said no so she grabbed a knife and went upstairs to cut herself (manipulation).
This sounds so familiar... .it's the same reason crisis in our house is so hard to deal with... .d17 (and now sd17 as well) turn their emotions in on themselves and we go through days/weeks of suicide watch. Just recently my h and sd spent a week with the flu that they likely caught while he was in the ER with her for suicide eval. We are lucky that it's only been self-harm and threats so far... .I'm afraid to even say that out loud in case I jinx it. Give me typical teenager rebellion any day!
It's quite possible that when your d turns 18, she won't actually leave if she doesn't have a plan for what that would look like.
Both our 17 year olds are eager to leave at 18 as well, I'll believe it when I see it. My d says she is going to live with the bf (she's pregnant) and they are going to get married. But he's older and still living with his family, no job, so I'm not as confident as she is that it will happen.
Sd17 thinks her parents are horrible people who don't deserve to have children, (she's not even speaking to her mother as far as I know) and she is going to leave at 18 and never look back. She has had a very sheltered life - so I sort of doubt that would work out either.
Neither of them have much ability to handle adversity, and living on your own on minimum wage requires a lot more hard work and toughness than they seem capable of.
I'm betting that home starts looking a lot better the closer those birthdays get.
On the other hand, telling them that would get us nowhere, so with my d I talk to her as if her plan is the plan. I'm happy to postpone the drama. Right now she's in a good place because she is living with the fantasy of life with her bf and baby.
Have you talked with your d about her plan for moving out? "You are really eager to get out of here, is there anything I can do to help you get ready for it?" You can talk about housing, insurance, etc. "Let me know if you want help researching insurance options." "I'm here for you whenever you need me, I want you to be safe." "What are your thoughts about a safety plan for when you are in the dark place?" "You can stay on our health insurance until you can get your own" Or whatever makes sense for you.
Sometimes defiance can be defused by putting them in control and offering support on their terms, but you would know best how receptive your d would be and how much you need to just take the lead and say "this is how it's going to be".
Here's to hoping that turning 18 will be a relief to you and your d... .