Should I confront the girl or not?

My daughter's father is talking to an EIGHTH grader! We are not together but I confronted him several of times about talking to young girls (hes 27!).He denies they did anything but in a text i saw today she said mentioned them having . I went on her fb and something in me thought she was younger than 17 which HE claimed she was. I found out a second ago through a picture she posted that shes actually FIFTEEN OR FOURTEEN! I think he knows it too and is just lying out his ***.I confronted her once and she FLAT out denied even knowing him so I know that he put her up to it or she was just smart enough to play it off. I want to confront her again but I want answers too! Im afraid she wont give them to me.The first time I confronted her I was very mature(no profanity,attacking,or anything) and I still didn't get the answers I was looking for.I do NOT want him i want to know because I despise men who take advantage or young girls and the girls that let them!!!!!