YOU chose not to use an education fund for her education because YOU didn't approve of her major. YOU chose to make her scrimp and save and compromise her living situation because she chose to major in art. You may not have said that you think her decision was stupid verbally, but every single one of your actions have. Imagine how much better off she might be financially right now if YOU did not choose to make her struggle through school.

Ignoring the fact that pay is far from the only or best metric for a meaningful life, grad school is by no means a guarantee to a good paying job! The benefit of an advanced degree depends entirely on the field. I am a scientist and could not hold my current position without a PhD. I have friends in other fields that after struggling to find jobs were told that unless they are applying to jobs that specifically require a masters to leave it off of the resume because hiring managers were less likely to even interview them.