What is the ruling on wearing a wedding dress that exposes the neck and upper chest in front of women only, and is wearing it, despite the transgression, considered a major sin that warrants punishment?

The 'awrah (intimate parts) of a Muslim woman in front of another Muslim woman is the area between the navel and the knee. A woman is permitted to look at another woman's body except for the area between the navel and the knee, similar to the case of a male mahram (definition). Therefore, it is permissible to wear the aforementioned dress in front of women.