I'd say let her be.
It's a very tough job market for anyone. I have former students working for near-minimum wage in all kinds of temporary and low-status jobs because that's what they've been able to get. I know they're bright and hardworking, but the job market is just not there. I would say it's actually realistic to believe that regardless of qualifications, she may wind up with retail. It takes a robust ego to handle serial rejection, too.
One way of handling it might be for her to seek extra responsibility and opportunity in the job that she's got, and prove to herself that she really is capable of these things. Again, though, that needs to be her choice, not yours. Support rather than trying to lead. Let her know that if she wants your help and support in seeking something more ambitious, you are happy to give them, but only if she asks. And if she does not, but complains instead, you can let her know (nicely and not in a bullying way) that while you're sympathetic, you would rather not go over and over the same territory, especially when you feel that there is a way out she's not taking -- and suggest doing something fun instead.