What is the word or term used to describe a person who intentionally ignores a rule/regulation/order
Scofflaw is a possibility:
A contemptuous law violator
Merriam-Webster.com
The term I would expect to be used for such a person is prima donna.
: a person who thinks she or he is better than everyone else and who does not work well as part of a team or group
(Source: Merriam-Webster)
If instead, you want to emphasize her lack of regard of workplace order, I would suggest insolent.
: rude or impolite
: having or showing a lack of respect for other people
(Source: Merriam-Webster)