How teenager defiled 3-year-old

The child of my friend’s sister, a three-year-old girl, was molested constantly by a 15 –year-old boy (names withheld), who lives with her grandma in Jakande Estate in Isolo, Lagos.
Her sister, who is married to a man from Imo State, has three children. She is not in the good books of her mother-in-law, but her husband liked to take the baby to his mother’s house wherever he  visited her.
They always stayed for some days. A 15-year-old boy lives with the woman, too, though I am not sure if they are related or not. She didn’t like the way the mother-inlaw treated her, so she avoided going there.
Her daughter, the victim, has always complained of pains in her private part, but she didn’t take it seriously. When the girl was using pampers, too, she always observed blood stains whenever she just got back from her motherin-law’s place. The few times she complained, the woman gave excuses. She then ignored it.
On two different occasions, the mother of the three-year-old had caught the boy telling her daughter to fondle his private part. Though the boy claimed the girl insisted and cried whenever he refused to allow her, she merely scolded and beat him. She thought it was nothing serious, she didn’t know it had gone far.
Last week, the girl was complaining bitterly and she decided to take her to the hospital. At the hospital, the doctor confirmed that her private part had been expanded beyond the usual. She was also suffering from slight bleeding.
Her mother became frightened and surprised, wondering what could have gone wrong. She later traced the abnormality in her daughter’s private part to the boy staying with her mother-in-law.
The doctor queried her responsibility as a mother, insisting that she wasn’t paying attention to her baby.
The hospital conducted other tests on the young girl and they found out that she was also suffering from an infection. Her mother wanted to inform the police right away and get the boy arrested, but the mother –in-law threatened her that she would drag her husband into the issue, too.
According to her, the man is also a suspect.
The girl’s mother is confused, she doesn’t know what to do at the moment. But she has stopped her daughter from going to her grandma’s place.