My mother is ignoring my family and her friends?

My background 37 years old, married for 8 years, have twin stepsons (13 years old) a 2 year old and another due in a few weeks. My father passed away in 2005 from cancer and my mother was understandably upset. She kept to herself for a few years and occasionally went on a few coffee dates but ALWAYS made sure she had time for her friends and family. She met a guy over 2 years ago and they have been dating exclusively since they met. When they first got together she would come over once a week (as we live in the same town 10 minutes away) call almost daily to see how us and the kids were etc.. Over time she has faded away from coming over, calling or doing anything with her grand kids. She has always said family first, no matter what. It is now April and she hasn't seen the kids since Christmas! I have called her about it and she makes up excuses like "I know I didn't like having my mother come over all the time" or "I hated when my mother in law would come over" (while talking to my wife)

I received an email from a life long friend of hers last week asking if she was still alive as he had been trying to get hold of her about his wife who was in the hospital for over a month by calling, writing emails etc.. I told him that he wasn't the only one trying to get hold of her. Today I was at my God parents house doing some work on their house and we saw my mother and her boyfriend walk by. My truck was in the driveway, the garage was open and they strolled by like they didn't know who we were. My God parents were her and my fathers best friends, they got my parents together 40 years ago. Obviously they were hurt as well, I explained that it has been like this since they got together 2 years ago. My Godmother called and left a message to have her call but doesn't expect a return call.

I am getting upset and embarrassed by her actions. I have tried to talk to her about it and she seems unfazed. Does anyone know what else I can do? I don't want to lose my mother but it seems I already have. A lot of her friends are my clients and I feel awkward trying to apologize for her actions.