I've met all too many designers and engineers who started out exactly like this, and years later come to realize that they've been underpaid by more than 50% below market rate for half a decade, and have little more to show for it than one entry on their resume and a case of Stockholm syndrome.
That's a home they could have bought if they knew their real value and weren't being exploited by a greedy employer. It's years of bitterness and job dissatisfaction they could have avoided by better knowing their value and having the right kind of ambition-inspiring peer pressure.
Let's assume you're not such a person, but at the same time I hope you would help educate your young designer about what exactly she's sacrificing by working with you at a salary of "making more than her mother." Please help her understand what she could be earning if she's willing to possibly relocate and hustle a bit, and allow her to make an informed decision.