"Thermofoil" cabinets are nothing more than low-end particle board (MDF) with a vinyl cladded exterior surface. Once the vinyl has been scalded and the vinyl warped that's pretty much the end of that product.
I can see where a heat gun wouldn't be the answer.
Those things are everywhere and I would think a replacement door could be located but as with a lot of things, the color may not be a perfect match over time.
She didn't buy the cabinets?
How about the builder, any chance a builder could be contacted to find out where the cabinets came from?