I am not a doctor so I don't know if what you describe is physically 'normal' or not.
But it sounds to me as though you are wondering if sexual abuse is taking place.
If her behavior is not the norm (in other words, it is excessive for the type of negative and selfish behavior most two year olds often present) and/or if it is the complete opposite of how she previously behaved, AND it is coupled with the physical evidence you notice then you are legally obligated to report your suspicions to the authorities.
I understand that you don't want to wrongfully accuse someone and bring discord to her family, but that pales in comparison to what may happen should your suspicions prove to be correct and you were to do nothing.
