Part of me thinks the only reason the OP is getting so much stick is because she is a stepmum. Because the amount of threads I have read on here over the past few years that insist all 16 year olds should work and fund their own lifestyle and pay rent etc (that are a little extreme) it seems unbelievable things have swung the other way and insisting that a 19 yo should be treated like a child!
The op isn't forcing her to move in with her boyfriend. She could move in with her mother. Alternatively, she could realise she's had an easy time of it so far, appreciate all she has been given, apologize profusely and sincerely, pull her socks up and start looking for work. I'm sure if in the next month she really shows hardworking and proactive the OP won't still go ahead - OP is likely at the end of her tether, and if the dsd starts behaving like the adult she is, may be kinder towards her.
No, parenting doesn't end at the age of 18. I've had financial help during my time at uni, and more recently financial help when I was on jobseekers. The difference is I was actually looking for work and trying, being unemployed was a hell not a holiday, and I know without doubt that had I not really been looking that help wouldn't have been there, or at least not so much of it. I am very sure my parents wouldn't have put up with me not looking for work for 2 years! Parenting isn't just mollycoddling though - it is preparing them for the real world too, and letting her stay at home indefinitely doing sweet FA would not be doing that.
As for 'revenge on the part of the adult' - DSD IS(!) an adult. You are an adult from 18. You can join the army, get married, drink alcohol, drive, vote, do many other things at 18 so at 19 you are definitely an adult! Not as mature as a 35 year old perhaps, but certainly not a child.
It's not like the dsd has spent the last two years searching for any job, attending interviews, and just been extremely down on her look. She's not hard done by. She has made no effort to find work, she has taken money she is not entitled to (because if her jsa advisor knew she'd not been going to interviews she would have been sanctioned), she seems to view being unemployed as a holiday and wasted the opportunities she's had for work which is sickening when you think of how many unemployed people get really down because of being unemployed, would give anything for an interview, and she's just wasting them. She's lazy, a layabout and workshy and completely NOT a victim of a 'wicked stepmother'.
God, with the kind of attitude on this thread I wouldn't be surprised if half the posters kids are still sponging off them at 40! You need to instil a work ethic on your children, that isn't done by letting them get away with this kind of shit. And you don't need to be 'horrible' to your kids to give them a work ethic - I was spoilt, never ironed til uni, didn't really have to work for my pocket money etc. But it was made clear to me that I had to work/be looking for work or be in education, as soon as I was an adult. Work ethic doesn't equal being horrible to your children to achieve that, as some posters clearly believe! I am shocked OP that you've let it go on for so long though.