What should my friend do?

Okay so my friend, is deciding what to do right now. A while ago, she and her friend that she liked used to hang out a lot, and at one point they even liked each other but they never went out. They always had problems and arguments about stuff. Now, mysteriously, he stopped talking and hanging out with her. It hurts her that he left mysteriously, and she wants to know if he still likes her or not, so she can move on. He is really hard to get a hold of and whenever he is on AIM, he is very uncooperative. What should she do?