This is so sad, I think this is where faith fails it's followers, it is healthy to forgive, that does not mean you need to minimise the sin, or even ever allow yourself to be around that person again, nor does it mean that that person is now someone you can trust, forgiveness should not be about making yourself, or others (like children), more vulnerable to further abuse.
All the 'I am not worthy' and 'turn the other cheek' teachings in faith are not healthy, it's such a complete shame to me that religion hasn't evolved as our understanding of humanity has, it sets up some followers as perfect victims, I'm sure the original ideas on being of a forgiving nature, were more about not carrying bitterness around, and therefore living closer to god, as in living with a feeling of personal wholeness and lightness of heart so that you were not inflicting your own hurts onto others etc.
.. and I say all that as a card carrying atheist. I think some people benefit from religion, however, in general it could do a much better job if it progressed a little (or a lot).