First, do not despair. Everyone knows that a woman's "no" is "Yes, but later". Seriously, the girls do quite often are distinguished by extreme inconsistency. Denying you today, tomorrow she might change her mind.
No need to refuse the offer of friendship, citing the fact that you love her and not be friends with her want. Saying this phrase, you may never see that will significantly reduce your chances of getting the girl. Accept the friendship and try to behave as a friend.
When a girl rejects you in a relationship, it is likely that she already has a favorite person. If so, her offer of friendship lies a great opportunity for you. Try to get close to her so that she began to discuss their personal problems. Knowing what she pleased, rather than dissatisfied in your young person, you will learn how to behave with her in the future.
Try to instill yourself as much as possible the traits that she likes and show those that may cause its rejection. Her boyfriend try not to judge or to give only constructive criticism. If you start to convince her that he was no match for her, then she is unlikely to tell you about a personal. In fact yet they are together, and your words will it hurt.
Let her know that you also have a personal life. It could reconsider its refusal, knowing that you might lose. Well, if she has to try hard to make you not just a friend. In this case it will be to appreciate your relationship.