I sort of think that the grief involved with losing somebody like Mom is immeasurable unless you are measuring gallons of tears. It is so wonderful that we all got to know her though. She was a very special woman, so dedicated to everybody else.
Nati, Dont feel bad. You did loads for Mom and you never know who is going when. You have to live your life. Dont think back, just forward. Mom can see you every day now and knows what you are doing (ok, not all the time).