The artistic temperament: open and vulnerable, riding waves of inspiration and feeling. Not exactly compatible with the mindset needed to close a deal. And thus we have the tension between Art and Commerce.
A similar tension exists in the brain. Some neural networks are associated with attention capture, where the stimulus rules. Other networks are associated with attention deployment, where goals rule. When one network is active, the other is suppressed. But no one network dominates for long; the baton is passed back-and-forth constantly.
That's a good thing, because doing Art and doing Commerce both require the dynamic and flexible interaction of neural networks. Both artistic and commercial endeavors require the ability to be responsive and goal-directed, porous and focused, disinhibited and controlled.
The Couple doesn't have to be unhappy. They just need to better appreciate what the other brings to the table and realize they are more alike than they think.