I think you want her to be like you.
But she is who she is. Their relationship is their relationship and how it works is up to them to figure out. Not that they couldn't take in a suggestion about mutual caring and concern and responsibility in relationships and setting mutual priorities, etc.
It is hard to know when to step back and let the chips fall where they may versus being proactive. A moot point maybe, but if they weren't under your roof this would be their issue alone to address. They have to decide what their priorities are, separately and as a couple, and how to ensure that those priorities are honored and worked toward, both separately and as a couple.