Most Helpful Girl
If the relationship has been good, no real drama going on, then I'd say she just needs some time to think things over. Don't contact her, and give her space. Respect her wishes.
You could send her flowers in a couple of days and see how she responds.
If the relationship has been on the rocks for some time or has been sort of unstable, in that case she might just have thrown in the towel on this one.
Usually it takes a woman some time to take a difficult decision, but this also makes it that more definite once she does. Even if it seems to you that she was able to cut off this relationship easily, trust me, she must have been checkign out emotionally for some time before.