ANSWER:

If this is to seek genuine guidance and advice to solve her problems then no problem, however if it’s just venting out then this is not permissible and it’s a major sin of backbiting.

Is it regarded as backbiting if a member of the family like mother talking to her son about her challenges with the father if it’s affecting her health and the husband is not giving listening ears rather making her go through psychological torture. This conversation may lead to talking about evil acts about the father and how to help it out.The woman health is at stake too.