My now 17 year old was saying (pretty much constantly, anytime we told her to do something thta she didn't want to do) "you know, I'll be 18 in July, and I graduate in June. I can leave whenever I want.".

She was making us both soooo irritated with this crud. So...
The last time she said it, I told her she can go. I wouldn't stop her, I'd even help carry her stuff outside. However, I told her, the money stops. There will be no graduation bbq, no $$ for prom hair/nails/grad bash, etc. She would need to find a job (she's been trying, but around where we are--it is bad--people with masters degrees are working at the mall and
walmart) so she could fend for herself. It would be just like it is for DD1--who gets a small amount of $ on her bday and Christmas (usually $50 for her Bday and around 100-150 for Christmas).
She was like no no no, I need the bbq and money. I told her if she made that comment about leaving again, that she WOULD be going, because I wasn't going to tolerate her attitude. It is affecting DS (he is starting to pick up her bad attitude and habits, and I am NOT going to go through that with a 7 year old boy).
In fact, she is grounded until next Friday--no one comes over and she is only allowed out for grad bash (and truthfully, if I hadn't paid $150 for it already, she wouldn't be going to it), because she didn't do the kitchen right. (I mean, she left dirty dishes unwashed, didn't wipe down counters and didn't sweep--because her boyfriend was here and she wanted to go over to her friend's house--the one that will let her live there if she leaves here).
this is a sticking point with me. I expect that things be done correctly. I'm not saying that they have to be done any certain way, just that they be done. If the kitchen is done, that includes all the dishes, counters and floors. If the bathroom is done, taht includes the tub, sink, counter, toilet (all the way from top to floor) and floors. No half-a**ing them. EDIT: this has been a battle with her for the last few months. I know she has "senioritis" and feels that she is grownup, but this is my home, and things will be done. It's not let she didn't do it correctly just once, and then we're punishing her.
I don't care if she is almost an adult--until she is paying rent in my house, she will follow my rules. If she wants to pay rent, well, then we'll work out a lease agreement and we'll go from there.
I am the meanest mom EVER!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!