The Office Pushover is the Real Heiress

Katherine Foden, a wealthy heiress, enters a company as an intern to escape an arranged marriage, only to be bullied in the workplace by a fake heiress, Kathleen who has stolen her identity and claims to be the fiancée of the CE0. Unbeknownst to her at first, the fiancée Katherine's father has chosen for her, David McGuire, is the CE0 of the company she's interning at. Later, she gradually falls for David as David falls for her as well.