Should My Mother Seek The Help Of A Professional?

My 22 year old cousin tragically passed away of a drug overdoes nearly two months ago, just a day after returning from a month long stint in rehab, which obviously didn’t do her much good. My mother was hit particularly hard by this sad and very unfortunate yet preventable occurrence, even though she and my cousin were never really that close. Their relationship was amiable and they would speak to one another at family parties, but they rarely if ever saw each other or interacted outside of family functions. Even two months later my mother is still shocked and saddened by the death of my cousin she can’t believe it, is angry and outraged and blames herself for not doing more to help prevent it from occurring even though there’s nothing she could have done. She also seems to be angry and resentful toward other family members including members of my cousins immediate family who although still grieving for her loss have sort of started to put the tragic event behind them and move on with their lives. I’m wondering if perhaps it would be a good idea to suggest that my mother see a professional to help her get over her grief? She talks about what happened daily as though it just occurred and seems depressed, shocked, angry and has trouble sleeping.