Empathy is really quite a self involved process that is about self and not the other.
When a child is in a new and unknown situation that is emotionally charged it will try and read how mother is emotionally reacting in its attempt to get a base line for itself.
A significant attachment figure was never fully internalised in childhood and thus there is a sense of a hole inside self. The therapist is used by the client to fill that hole.
Anger is a distancing emotion it pushes people apart. When people want distance in a relationship anger can be used to achieve this