I am in a similar situation with my 37 year old stepson. In my case there is NO way we would boot him out as he has depression and I believe he isn't capable of holding down a job.
The trouble is, if you give any ultimatum, you MUST mean it. But without any practical sanctions you can AND WILL enforce, there is no reason why she would do as you ask, unless she chooses to. If you would knuckle under if she calls your bluff, don't threaten it in the first place.
Let's say you tell her she must leave in 3 months, or even a year. The day comes and - ooh, guess what? She still has no job and no new home to move to. Are you actually prepared to change the locks while she's out, or have the police escort her off the premises if she refuses to go? Would you really refuse to give in if she burst into noisy sobs and said she had nowhere to go and would do housework from now on? I suspect few parents would be that harsh - and I'm certain you're not one of them!
So if you're going to demand that she helps around the house from now on, how will you enforce that? If you're going to charge her rent and add the amount to what she owes you, how will you make her give you that money if she says she can't pay? How will you force her to sign on for jobseekers if she isn't willing?
The Wi-fi sanction idea is good - she can certainly go to the library and search for jobs, or even the job centre. You could also remove all your furniture bit by bit from her room - it's yours, you don't have to let her use it!
The bucket of water - well, that's assault, surely?