If he still calls your friend frequently, I would say he still holds much affection & concern for her. If he didn't care, he would not call or contact her.
What your friend needs to understand is that he is married. This means it was a forbidden relationship between this man and your friend to begin with. His ultimate duty is to his wife and family above all else. There are only two things that can happen here. He will have to choose which side to be on, your friend's or his wife's. He chose the wife. An honorable man would not have an affair outside of his marriage, he would only be with his wife, and not others. In cultures where multiple wives are allowed, the FIRST WIFE has much power to influence the husband because she is the first. So all other wives that are brought into the family unit will be subordinate to her (below her in status and power). I don't know what culture your friend is from.
Also, to keep a family together, a man will often stay with the wife to protect his reputation, his money & assets from divorce, his children's emotional well-being, and status. Divorce is an ugly thing, and can ruin people financially, their reputations, devastate children, and cause much conflict in the extended family. Many married men will have affairs if they think the wife will not find out. But don't EVER believe that they will leave the wife for good until the divorce is settled by law. Arranged marriages are the hardest of all to break, because this culture will cause problems for the man's reputation. As he accepted to marry her, he also accepted the duty and responsibility to stand by her and the family.
In any culture or circumstance, the chances of the man leaving the wife are few and difficult. It's easier to stay with the wife than to risk the break from her. It is also just a way for men to have affairs and never have to commit to the other woman. While his heart may be hurt, he must do what his duty is-and that is side with wife & family. A difficult lesson your friend has learned, and she must move on. In the future, she should never get involved with another married man, or risk this emotional pain again. He was never hers, he belongs to his wife, regardless of where his heart lies.... unless he divorces the wife.
Now, think of this: if he found it ok to cheat on his wife, why would your friend still want him? Could she ever trust him not to cheat on her too? She is foolish to think that he is trustworthy, honest, and honorable if he ignores the bonds of marriage to be with another woman. The only way he can prove his love for her is to divorce his wife, or let your friend go to persue happiness for herself. Marriage is supposed to be sacred and pure for a husband and wife. He desecrated his marriage by bringing another woman into his life, his marriage, and is wrong for doing so. Your friend is the one who is hurt and feels rejected... and this is how almost all affairs will and do end up. It is not worth it. Best thing to do is to forget him, don't communicate with him, and live her life. Find a man without a wife or girlfriend, and who will be trustworthy, and deserves her heart. The married man doesn't deserve her, he has a wife already, and chose the wife over her. That is a clear sign that this was not meant to be. He may love her, but not enough to choose her instead of the wife. He fears risking everything, and finds it easier to stay with his wife... which, like I said, is his duty unless divorced.