I havent had personnal experience with mites either, but I know enough, to tell you that your friend has no immediate need for panic! hehe.
I know the affects of mites are worse, depending on the size of the snake, the smaller the snake, the greater the affects of blood loss through the mite infestation.
Do you have Kathy Loves book on corn snakes, if so, many possible solutions for removing mites are described, for example rinsing to start the removal process. I'll quote some of the book for ya
"Place the infested snake in a plastic jar or box filled with water to a depth thast higher than the snakes girth. The lid should be perforated to allow for air flow" (Love, K., 2005).