Unfortunately labor laws are almost exclusively governed by the state, so only Ohio residents (of which I'm not) can give you specific advice. But here's some general advice -
First, these people are assholes, so you daughter shouldn't be thinking about trying to get her job back. Instead, she should think about dicking with them and maybe getting a little money out of the deal.
Go down to your local state offices or Labor Board and pick up all the info you can relating to firing, minors, and Worker's Comp. Your daughter can probably file claims/complaints on several points:
It may not have been legal to leave her there all alone and make her work that number of hours or that late at night. They might pay penalties for that.
The fact that she was fired because she was trying to file an injury report is important. Many states (like mine) impose extra special penalties for termimating an employee over a work injury. Ask for a Worker's Compensation claim form from the state office and get medical treatment!!
Start talking to [url=http://www.subway.com]Subway[/url] about the illegal labor practices of their franchisee.
But first, before you do anything, talk to a lawyer. They work on a percentage, and many times just a call from an attorney and the company will roll over $20k or $30k just to get a signed release. The lawyer gets $10k, your daughter gets a new car, and Subway pays higher WorkComp insurance premiums for years that comes right out of the owner's pocket.
The fact that it was the manager's boyfriend that flaked and she was fired for trying to submit an injury report all work in your daughter's favor. It's very possible that the owner doesn't know about all this and when he gets the bill, he will probably fire them immediately. More payback!
I've been involved in a couple of work injuries in my 20+ years in the workforce, and I can tell you that every time I tried to go it alone I got screwed. Now I call my attorney right away and nobody messes with me. Christ - if that happened to my daughter, I'd own that Subway by now!!
So don't let them get away with it! Open those yellow pages right now and pick out a lawyer that specializes in Work Comp (look for the biggest display ad), and start filling out paperwork! It will cost you absolutely nothing, and it's the only way you'll ever have to get back at the assholes that mistreated your daughter.