I don't know how to help, a part from saying a little prayer for her. I'm just shocked with how much this lady had to deal with. Please send my deepest sympathy for her loss.
Her Family Liaison Officer should have given her details of who can help, specially her son being ivictim of murder. I don't know of the circumstances, but she may also be at risk.
There is a green A3 (used to be) victim compensation form. This is a standard form that is used from day to day muggings to murder. Again, I don't know of the circumstances, but she may wish to claim any expenses of counselling, work days lost (and wages), funeral expenses, etc through this form. The loss of a life can never be replaced, but at least she won't have to worry about her financial situation whilst going through the grieving process.
If she is not happy with the assistance (or lack of it) that her FLO is providing she (or a friend/relative) can complaint to the Association of Chief Police Officers and to the Force's Chief Constable - make a letter direct to them, with their name printed on it otherwise it might end on less fruiticious hands. Google they site and it will give contact details.
All the very best and well done on you for trying to help her.