It sounds like a cafe-au-lait spot. Is it flat?
Here is a link to more information about cafe-au-lait spots.
http://www.rainbowpediatrics.net/cgi...unction=logout
http://my.webmd.com/hw/health_guide_...p?pagenumber=2
For cover up information. Look under the PWS discussions. There are makeups that people recommend for covering PWS, might work very well for her spot, if you feel it needs to be covered?
Corinne