Is it permissible for a woman to go to places designated for women, without knowing if the place is free of immoral women who might transmit or describe 'awrat (parts of the body that should be covered), and with the possibility of hidden filming?

Doubt concerning the presence of surveillance cameras does not affect the ruling unless it is based on evidence. If it is highly probable that the place is free from immoral women, men, and photography, then there is no objection to a woman appearing with her adornment while covering her awrah in front of other women. The default assumption for Muslims is safety. However, being cautious in this regard is better and closer to piety.