I think if your friend is really in love with him, then she should try to win him back. If she has exhausted her efforts in winning him back and still he won't come back, then this will only show that he is no longer interested and a sign for your friend to move on. At least she won't have any regrets because she did try to win him back but failed instead.

I found some tips which might serve as a guide on how to win him back. You can read the full details at the source.

----quote---
1.Demonstrate that you've learned from past missteps.
2.Remind him, through your actions, why he fell in love with you in the first place.
3.Be there to support him.
4.Win over his friends.
5.Reminisce.
6.Think of the pastimes and activities that were central to your former relationship.
7.Look your best.
8.Be positive.
9.Don't be too obvious in expressing your desire to get him back.
10.On that note... your strategy should be to start in the realm of subtlety, and slowly turn up the heat.
11.No drunken phone calls!
12.Do you really want him back?
---end of quote--

From a male standpoint, I guess she could try to be friends with him again. Try to win him over by being there for him whenever he needs her. If she'd beginning to fall for him, I'd say that she's having a hard time to move on. Give it another try. Love is sweeter the second time around, they always say. If she really loves him, then do whatever it takes. I hope this helps.