ual charge question?

ok here goes the question..... my cousin and his gf are 18 and 15. they got together in high school he was a senior and she was a freshman. and for all of you who think that is a big age gap it isnt and he treats her real good and has never cheated on her or nuffin. now her mom doesnt want them dating and she logged her IMs and saw that they had talked about trying to have and having . now i know this is wrong ok i kno so please no answers about this being a bad thing i already know that. what i want to know is can her mom press charges if it is legal for them to have but they talk about it over the internet. is this ual solicitation of a minor or is it something else. thank you