He isn't lying when he tells himself he loves her.
He hadn't been looking for her, not exactly. He had been looking for a fertility specialist. It was the island that had been looking specifically for Juliet, Jacob who was certain she would come.
Ben had been told that Juliet would prove very important to him, and so he would have gone out of his way to be welcoming to her even if Mikhail hadn't shown him the picture Richard had sent. It wasn't that difficult to welcome someone who looked like her.
His heart had fluttered as he met her at the dock, and a queasy anticipation gripped him as he saw her climb out of the submarine, blinking against the brightness and looking delightfully innocent and naïve. He had missed innocence. In more ways than one.
As he lies awake that night, staring at the ceiling, he decides the queasy feeling is love, that that is why the island has brought her here. She is his reward. He feels a surge of gratitude towards Jacob and cuts off the thought that it is about time he had a reward, especially since Alex is growing up much too fast and the hero worship is no longer present in her eyes when she looks at him.
Calmly, clear-headedly, Ben begins to lay out his plan for winning Juliet's heart. He isn't too worried, as every sign indicates that she belongs to him, but he plans, anyway, out of habit. He'll be charming and endearing and she will love him as he loves her.
He isn't lying about it, but it still isn't true.