Time for some Intersex Fun Facts with Lyudmila!
The mother in the article described as having cells from two individuals has an intersex condition called 46, XX/46, XY or tetragametic chimerism. The arrangement of the differentiated cells in her body will follow a mosaic pattern, identifiable on the skin level along Blaschko's lines.
Some chimeric individuals may even have a visible striped pattern of two different skin tones, but it's typically only visible under blacklight. Here's an example of a mosaic skin condition which shows one of these patterns in a visually apparent difference of skin tone along Blaschko's lines. The individual photographed may or may not be chimeric, they have a skin condition unrelated to chimerism: