Is it permissible for a working woman to combine the prayers she misses due to the unavailability of a place to pray at her workplace, given that her living conditions necessitate her working?

You must perform the prayers at their appointed times. If there is a genuine necessity that prevents you from performing the prayer on time, it is permissible for you to combine the prayers that share a common time (Dhuhr and Asr, Maghrib and Isha), because the fear of livelihood detriment permits combining.