I think you're going to just have to tell it like it is.
"It's great that you and *insert boyfriends name* are getting on so well! I've been reminded by *landlord* that we're only officially allowed to have 3 people here, but we can fix that! Let's sit down & divide the rent & bills into 4, and get him on the lease"
If she brings up the fact that he doesn't have a job, tell her well that's okay, she can pay his share until he finds one, & he can pay her back. It shouldn't be too long right?
It's going to be hard, and yes, she will probably get angry, but you can't let the situation go on and on.
i agree, you need to tell it like it is to her. all three of you should sit down and lay some groundrules about people's partners. because it's not fair her leaving thus guy in your home running up bills for you, maybe eating and drinking your stuff and plus can you trust him not to go into your room and start snooping? it's just not on really. i hope it goes ok for you.
At the very least, he could clean up after her. It's not as if he's doing much else. In a way I can feel some empathy for him, as there is scant hope of finding a job (for most people) if you do not already have one now. That said, he is not officially a tenant as the landlord and the other tenants have not acquiesced to his residency.
But he should at least be cleaning up after her mess. And he needs to start paying his way for starters..
it seems like whether he does her dishes is between the two of them; more related to how he can pay her back for extending upon her resources (which she may or may not care about)...ultimately, her dirty dishes are *her* responsibility, whether she does them herself or makes arrangements for someone else to do it for her.
i think you can bring up the point that the rental arrangement has changed without your consent. assuming that you three split the cost of the home in total, it is unfair for one party to introduce an unpaying tenant into the mix, using resources (space, electricity, cable) that you are not compensated for. maybe have a household meeting where you talk about how this guy can either leave, or begin paying a quarter of rent and expenses.