I find pets develop that bond with humans much like we have for them.. and when their "love" is gone... they soon leave to join... for me.. thats love.. few truely experience a love like that.. its not that they were a part of your mother, but she was also part of them..

I feel for your loss.. but feel something of comfort to know that she was truely loved not only by you and family... but the two who were her costant companions.. and together.. they all are in a better place..