What is the 'awrah of a Muslim woman in front of Muslim women, and is uncovering it in front of them considered a major or minor sin?

The 'awrah of a Muslim woman in front of other Muslim women is the area between the navel and the knee. It is not permissible to take lightly the uncovering of the 'awrah, even if it is a minor sin, for a believer should not take any sin lightly, no matter how small it may be.