Help. My 18 yr.old daughter has been waylaid by a 27 yr.old?

This man was/is involved with a woman and they have 2 kids. They were living together and just had a baby. Some how he set his sights on my daughter and left his wife and decided he wants to be with my daughter. She is infatuated and believes all that he tells her and blames his 'wife' for the split. I have been in contact with the wife and am given her side of the story. It seems this guy is a cad and is lying to both of them, however my daughter won't consider the wifes side and thinks everything the wife says is a lie. She is being manipulated, lied to ,and God knows what, how can I help her see that this guy is no good ?