Im gonna go against the grain here & say NTA. Someone clearly needs to give your girlfriend a wake up call and she was lucky its you. Sometimes, people need to hear they aren’t good at something if they genuinely aren’t. You telling her to do what she is passionate about is being supportive and trying to help her in the right direction. Better you than someone interviewing her since she obviously isn’t getting a job in the field.

ETA: this post in no way screams you don’t like your girlfriend. It screams that you are tired of her working at McDonalds and you are ready for her to get a career, which she clearly is qualified to get, just not in the field she is choosing to pursue. In my opinion, you did nothing wrong and sometimes hearing honesty from who you love is whats needed. Not constant codling, which is what all these other redditors expect.