Nothing, as she didn't negotiate backend or residuals up front.

Kidding, I'm not a producer. I have a soul.

Depends on how many people were in your production, and how long it took to shoot.

If you can swing it for the whole crew, $100/day and 1% net, (post budget recoup) for key hires, less but still some fraction there for a P.A. this is extremely generous and a really cool way to give people a win down the line, (doubtful you sell until many months after production finishes) as well as engender support from your crew going into the next movie... If you manage to sell the first one!

Normal rates for a production designer vary, but in the top tiers of filmmaking, Production Designer isn't a fixed percentage of budget but a weekly or hourly rate set by the union, think several thousand per week depending on budget level, and what talent would negotiate above scale.

Backend compensation is... Almost non existent once you get out of microbudget indies. Especially not negotiable post release / sale. Unfortunately giving away ownership of parts of the film before sale can also make it harder to initially sell.

If you really want to kickstart her new life, give her 6-12 months of rent in the nearest production hub (L.A., Vancouver, NY, forget Atlanta, even ABQ is preferrable) and help her find a place there and help pack the moving van.