Each person in your family has a unique relationship with your mother, so each of you will grieve her in a unique way. Also, each of you is unique in how you cope with stresses. These ways of coping apply to grief also.

Sometimes grieving starts before someone dies. This is known as anticipatory grief. It seems that your sister is going through this. She’s facing the added challenge of working through her grief while she’s also helping care for your mother. This experience may be overwhelming her, and it may be hard for you to watch her go through it.

Your sister’s anger is part of her grieving. Even if she’s irritable, impatient or openly hostile toward some of you, her feelings may not be directed at anyone in particular; sometimes it’s just safer to vent feelings with family members. Your sister may keep you at a distance and keep you from helping her. All of this may be easy to understand in theory, but it’s hard to accept emotionally. The best you can do is just be there for her, and be ready to talk with her when she’s ready.

Talking about feelings and what’s behind them can be therapeutic, but some people may be more comfortable talking to people outside the immediate family. Your sister may prefer to talk to a trusted friend or a spiritual care provider, who can be a valuable source of support.

Many communities have support groups, bereavement groups, or other resources that may be useful to members of your family. You may want to look for a social worker who can offer counseling to your sister or others in your family, or can help you find other useful support and resources.