Her job is already going away; McDonald's around me have already replaced cashiers with kiosks. Unionizing and requiring $15/hr + full benefits is only going to accelerate McDonald's automation plans. Is the answer to fight for $15/hr or is the answer to go back to school, apply to more jobs, and/or go into a trade? Honest question.
There are places in the world where you can make a living without any particular skill set, but I don’t think the US, or any other first-world country, should really be among them.
The US needs immigration reform to bring more high-skilled people into the country, but it also needs emigration reform to find new homes for people who can’t necessarily make a reasonable living in a first-world country.