One Little Mix Up: A Second Chance, Office Romance (Office Escapades Book 3) by Robin Edwards

Great Office Escapades book. Trevor was born with a silver spoon in his mouth and never wanted to give it up. His parents decided he had to work a little and show some responsibility before they gave him his inheritance. Trevor was lucky his uncle owned a company and agreed to let him have a trial period to see how things go.
Beth's mind was made up, she would never settle down from partying or with a man. She was happy with the way things were going in her life. She has had a couple really nice promotions at her job and was enjoying all parts of her life. Until Trevor started and announced he wanted Beth to train him.
Now they both were spending time together and falling for each other.