Perhaps this is because you truly care about the woman, and this child is part of her, and likely somehow reflects her in it's essence, as well.
If you were drawn enough to her when you dated, you may then have also wondered what it would be like to have a family with her . . .
I am guessing you actually may have relatively strong feelings toward the woman?
Of course, we are assuming this child could in no way be assumed to even possibly be yours, since you say she was "raped"?
Could the woman be depressed? There is what is called "post partum depression", and pretty likely in this situation. Perhaps she is suffering from this?
It sounds like you really need decide how you feel about this woman. If the child is safe with the grandparents, that's good.
Are there feelings yet to sort out between the two of you? That may be the point you need to concentrate on, and especially since she is "running to you". The baby will likely be fine where she is. You have to decide how you feel.