Is it permissible for a working woman to remove some of her clothes for ablution during working hours, and what should she do if prayer time conflicts with work, and is it permissible to perform the prayer before its time for someone who wishes to leave and will not return until after the time of the next prayer?

Delaying prayer beyond its prescribed time is a grave sin. Work is not an excuse for delaying or advancing it, unless there is a valid concession for combining prayers due to a permissible reason.

If you fear harm to your livelihood and cannot perform the prayer on time without exposing your awrah, then it is permissible for you to take the concession of combining Dhuhr with Asr by delaying it (jama ta'khir).

If you can perform ablution and pray on time without exposing your awrah in front of non-mahram men, then this is what is obligatory. You can lighten your clothes for ablution if you are safe from being seen, and utilize concessions such as wiping over socks and a head covering if they were worn after purification.