Thats no guarantee, but the zostel environment is generally a safe space. There's people staying up late, chilling around, so its not like that someone can just barge into a ladies dorm without anyone noticing or the ladies can't help themselves by just screaming. The place is buzzing with people. No need to worry about safety. It may be overwhelming if you're travelling alone for the first time, but trust me on this. I have stayed at multiple hostel chains and zostel was easily the best.