Alpha's Rejected Omega Mate

[Mallory's POV] On my 18th birthday eve, I was sleeping in bed when a deep voice whispered in my left ear, "Mallory..." "Hmm." I tried to turn and push the figure away, but the person looming above me yanked a handful of my hair. "Ah!" My eyes snapped open, and I saw who was above me. Ace Lennox. The Beta's son. "Ace... What are you doing here?" I asked him as I gazed at his honey-brown eyes. "Shush..." He hushed me by placing his thumb on my pink lips. "I came to see how you're doing. It's your 18th birthday tomorrow. Don't you think you deserve a birthday gift?" Ace asked me as he stripped off his white top. "What kind of birthday gift is that? Why don't you wait until tomorrow to present it to me?" I asked him, but he shook his head and replied, "No, Mallory. You deserve to have the gift tonight. It's very special, and I have been keeping it for you." "What is it?" I asked him, looking at his handsome brown face. Ace was the Beta's son. Even though I am an Alpha's daughter, I lost my respect because I haven't shifted since I was born, and my younger sister, Sonia, has been able to shift since she was fourteen years old. Everyone in our pack looked up to Sonia while they overlooked me. The worst part was that Sonia seemed to bask in it, and she made it look like I was the bad person. I loved Ace and wanted to be his mate, but he didn't speak to me during the daytime. He mostly avoided me, and I wondered how he was able to sneak into this room and into my bed. My room was on the top floor of the magnificent two-story building that was the Alpha's mansion, so it amazed me that Ace was able to get access in here. "I want to give you a priceless gift, Mallory, but you must promise me that you won't shout and you will endure it," Ace said, as he removed his trousers. I gulped hard, seeing his full broad chest, his strong masculine abs, and I felt the urge to touch him. I knew that Ace was going to be my fated mate tomorrow, and I was wondering what the birthday celebration would be for me, since my father didn't like me. "I want to sleep with you, Mallory. Just don't shout, alright? I want you as much as you want me too," Ace said, his brown eyes glowing in the darkness of the night. "Alright." I agreed. At this point, it warmed my heart to see that Ace wanted me. I knew that everyone in the pack looked down on me, but seeing that I had someone who didn't made me happy. "I know that we are going to be destined mates. I want you, Ace," I told him, caressing his chest, and he brought his face closer to mine. Ace kissed my lips passionately. He was a 21-year-old man, and many girls in our pack crushed on him. Even Sonia, my younger sister, hoped that by the time she turned 18 years old, she would become Ace's mate. Sonia and I are only a year apart because my father had married her mother after my mother died giving birth to me. We were half-sisters, and my father had to take up another Luna to help protect our pack. My mother was an Omega who happened to be my father's true mate, and when I was born, the pack doctor told my father that I was an Omega too. A weak link of the pack, which got him disappointed. To make the matter worse, I was unable to shift like the rest of our pack members. I was short and not as tall as Sonia. She was tall, light-skinned, and very beautiful. I wasn't a dwarf, but I was of average height and not as tall as her. It hurt me that no one wanted me, but seeing that Ace wanted me and I knew that he was my fated mate, I agreed to make love with him, hoping that he would give me the best birthday gift. Besides, tomorrow was my 18th birthday party. "Are you ready?" Ace asked me, as he was now fully naked on my bed. "Yes," I replied, swallowing hard and not believing that I was doing this with him. He had taken off my nightdress and left me fully naked on the bed with him. I moaned, breathless, and Ace prepared himself to thrust into me. By the time he crossed the bridge and thrust into me, I moaned and cried, and he didn't stop. Ace kept on with his actions until I was about to faint. "Damn it, Mallory! You're so tight!" Ace kept on with his actions, and he brought his face to mine. "You're mine," he said, burying his face in my neck, and he brought his fangs out and bit me. "Ah!" I groaned, and Ace climaxed inside me. After a while, he pulled out and licked the spot where he had marked me on my neck. "I have to go now, Mallory. Happy birthday to you." Ace kissed my lips and dressed at lightning speed. Just as I heard the sound of footsteps approaching my room door. The door burst open, but Ace had already fled out the window. I wondered if he didn't break his leg, and then my stepmother, Luna Lily, came in. "Mallory, what are you doing on the bed, nàked at this time of the night? Were you the one moaning?" She marched up to the bed, met me, and yanked away the bedsheet that I had used to cover my chest. "Mallory, you bìtch! Who were you f*****g in your room?" she growled, dragging me by my arms, and not minding that I was unclothed.