We process events individually and ones response to an event can be very different from another's response to an event.

I'm not big on suggestions but is this a coping mechanism to shut things out so you don't feel emotional when something happens to a family member?

I sense some disconnect when I see the word animosity used when describing your feelings towards your mother. You've stated that she hasn't done anything (that you are consciously aware of) so it's left me wondering what other circumstances are going on that may contribute towards your feelings.