I agree with Precious Pearl on this. Losing a child has got to be THE worst pain imaginable, universally, in the human race.
God had nothing to do with her baby's death, so it wasn't for a greater good. Beleiving that God took her baby for any reason whatsoever would be a really good reason NOT to forgive him. He loves us and wouldn't want to hurt us. That logic is insulting and would only deepen her resolve to blame someone for this terrible loss. I don't know the conditions by which she lost her baby, but regardless, iti s due to our imperfect human condition.
God didn't intend death. Death was brought about by sin when Satan first introduced it to Eve in the garden of Eden. God would never intend for a mother to lose her child.
Love her and hold her and let her cry on your shoulder. Let her draw strength from you and others she surrounds herself with. But I would caution against trying to tell her how she should feel.