See the thing is she's a psychologist...she should know how to handle death and her own feelings.
Unfortunately, it doesn't work like that.
Dealing with death on a professional level is not the same as dealing with the death of someone you know personally.
It's also true that you can't compare your Nana's grief to yours, but you can't judge how people should react to grief on the basis of their biological relationship to the person. Some people just react better than others in bad situations. And some people tend to lash out at others when they are feeling bad. That doesn't mean it's right, it's just the way people are, and once they get to a certain age, there probably isn't much you can do to change them.
Reeka, I'm sorry for all you and your mom are going through. The only advice I can give is for you both to maybe take some time out each day to meditate, exercise or do some other stress-reducing activity. Because, Reeka, you can't change the way that other people are, but you can change the way that you react to their behaviour.
hugs.
Edit: Just noticed you said you were going to go to grief counseling. I just did this and it was very helpful.