She's 18 and she won't shower?!?! Regardless of what she's been through, perhaps someone ought to tell her to grow up a little. Does she not realise she pongs or that he hair looks awful?
As to getting a job, does she get pocket money from your brother to go out etc etc? Perhaps cutting that off until she makea a contribution would change her attitude. If she doesn't like going out, stop buying food she likes, magazines etc until she pays her way a little.
Perhaps your brother ought to talk to her other 'dad' about this, and try and find out what went wrong between the two of them. If it's thge same thing (her general attitude) maybe she' s trying to play one off against the other, which they may need to unite over to beat this.