Suspecting daughters friend is being sexually abused

My 9 year old daughter had her friend over for a play date. While in her room the friend told her that her guinea pig would get pregnant if she did this ritual, which included rubbing the guinea pig's belly on her vagina. When my daughter questioned it her friend said she had seen it on a website and that she must do it everyday until the guinea pig is pregnant. Her friend would not watch but questioned her for a few days if she was continuing with the ritual. When she kept telling me she thought her pet was pregnant I assured her it was not possible and that is when she told me what her friend had said and asked her to do. Is this just a bizarre situation of peer pressure in getting my daughter to do what she says or could this be a sign that my daughters friend is being sexually abused? If so, how should I handle this? Should I question her friend further?