Your Gold Digger is Actually A True Heiress by Vera Fiore

Thalia Winters has always been the devoted girlfriend, but her world is turned upside down when she overhears a conversation that shatters her trust. Her boyfriend, Drake Ashcroft, has been using her as a mere stand-in for his college sweetheart, Sienna, who has just returned from Paris. Heartbroken and betrayed, Thalia decides to stop resisting her family's wishes and agrees to an arranged marriage with the powerful Asher Blackwood. As she uncovers more about Drake's feelings for Sienna, Thalia realizes she was never truly loved. The final blow comes when she sees Drake flaunting his new relationship at a social event, completely oblivious to her presence. With her heart hardened, Thalia resolves to embrace her true identity as an heiress, leaving behind the man who failed to recognize her worth and stepping boldly into a future she can claim for herself.