Sounds like your brother and his wife over compensated with their daughter because they had a tough childhood and wanted her to have everything they didn't. As for finding it hard to get work - I think we've all been there - finding the right work for you has always been hard, you're very lucky if it's easy! As a first or second job you have to take what's going and then move forwards so any job is better than none at all. Wonder if she's been aiming too high?

There is only one answer for how to get somoene to move out and that's to give them a deadline and not be swayed. If hints haven't worked (or have been ignored) an ultimatum is the only way.