Is it permissible for the bride to wear an immodest white dress (without hijab and showing her arms) in front of women only?

There is no objection to a woman wearing trousers and a blouse in front of other women if they are not form-fitting and not transparent, as long as no fitna (temptation/strife) results from it. This is because the 기본 (original ruling) is the permissibility of a woman looking at another woman, except for her awrah (private parts). The awrah of a Muslim woman to another woman is like the awrah of a man to another man, which is from the navel to the knee. This also applies to a non-Muslim woman.