The following is snipped from a mental health site....Bolding is mine.
How Does Grief Affect a Person?
People deal with grief in extremely diverse ways and often this can make the person offering support uncomfortable. Despite individual uniqueness, usually an overall pattern does occur, understanding this may help you to show compassion during the different stages of grieving.
Grief often begins with shock and numbness and possibly denial. This is usually followed by a time when the pain sets in. Strong emotions may overwhelm the person. Commonly during the sadness following bereavement, the person may have no energy and feel listless. They may withdraw or have mood fluctuations, and this can be the hardest and longest period of the grieving process. Finally, there is acceptance as the loss is accepted - although this is not necessarily a happy acceptance. Energy and hope begin to return.
The entire process is different for everyone and it is never orderly. Grief may return and be particularly painful around the times of anniversaries, birthdays, family get-togethers and Christmas times when the person's absence is all the more obvious. It is impossible to say how long the grieving process lasts. It will vary greatly depending on the relationship and nature of the death.
Ways to Help
Things that are usually helpful:
Allow Grief
It can be difficult to watch somebody go through the grieving process but it isn't helpful to give the person a message that says 'chin up'. It is important that the person does grieve. According to research, unresolved grief can lead to outbursts of anger and rage, restlessness, depression, addiction, compulsion, anxiety and panic disorders. Physical symptoms can include worsening or developing diabetes, heart disease, hypertension, cancer, asthma, allergies, constipation, diarrhoea and ulcers. Don't allow your discomfort with the person's grief stop them from expressing it.
Be Supportive
Many people hold back as they are afraid of saying or doing the wrong thing. Rest assured that the person grieving doesnt expect you to know what to say. It is generally felt that the important first step is to acknowledge the person's loss. If you don't have the words a hug can speak volumes. Accept the person's grief and offer your supportive presence even if this makes you uncomfortable. Don't be afraid to talk about the dead person and share your memories of them, if you knew them.
Make allowances
Some grieving people may exhibit some (temporarily) unusual conduct that affects relationships and everyday activities: isolating themselves or on the other hand, not wanting to be alone
resentment that others aren't grieving
critical or irritable in ways that are out of character
odd events, which seem real, like sensing the presence of a loved one.
If the person is worried it may help to know that these things, are a lot more common than they may think. For example, it is common to 'hear' the voice of the deceased person or to 'see' or 'feel' their presence. If you are concerned about how the person is grieving, it is a good idea to speak to a GP or grief counsellor.