Sadly, my gut instinct says it would be strange for a 9 year old to feel comfortable rubbing a guinea pig against her genitals, let alone speaking of it. I think she is well old enough to know better, and also just a girl would feel innately averse to such action. I can't be sure. This is very, very wierd. Child protective services are a resource, they are not always that good. Perhaps if they are in the same class at school with a good teacher, asking the teacher to look for signs as well might help.