OK this girl is really a PILL. She and I got in a spat over a misunderstanding several months ago.?

Nothing serious at all but she can't seem to forgive any one ever and holds lots of sour grudges. Anyways, she started dating one of my friends Logan (who my family has known for over 17 years) (who consequently I had introduced to her at my b-day party). She told him all kinds of trash about me and my family. So now Logan won't even speak to me nor will she. They both are being extremely rude and yet when she sees me she just grins. Logan's parents told my mom that he has spent over $30 in text messages just to her. What I want to know is why he would pick her ( who is not smart, ugly, and rude. ) insted of someone they have known for a very long time.