Most Helpful Guy
Tell them that divorce is a lot more expensive than it would be if they just figure out what's wrong and fix it. They loved each other enough to get married to begin with, they just need to find those reasons again and from there, find the energy to get over what is causing their problems.
Most Helpful Girl
You can't make them stay together, staying together while they're miserable and always fighting isn't good for your family, it'll just create more tension and stress. Now if you wanted to suggest marriage counseling to your mom that could be an option but otherwise there isn't something you can really do.