Verrucas are Warts that appear on the
foot, that much I know. The scientific name for the virus is the
Human Papilloma Virus which I think comes in about 60 varieties affecting the vaginal, oral and other areas and that it can take several months, since infection, for the verruca to develop, with no visible signs.
She might well have an infection and not know about it; because it can take anything up to 20 months to develop.