How can I get through to my little brother?

My brother is a very kind man but his long distance girlfriend is completely toxic. He works at a factory for 5 days a week 50 hours a week while going to school for nursing. The poor guys up 19 hours a day 5 days a week. His lazy unemployed girlfriend keeps saying if he was going to get a degree he should of by now 30 and is to old to be in school. When she knows he dropped out of highschool at 17 to raise our eldest sisters kids cause she's a moron and it wasn't until last year that he was able to go back to school. I've tried several times to tell him he can do better but she keeps getting in his head saying no one would want him I need advice to help him see how bad she is for him. Any advice would be greatly appreciated.

How can I get through to my little brother?
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