"But…I'm right here," he tells her, not just confused but a little tired of his friends making these kinds of comments, the ones that don't make any sense. He really is him, and he's right here.
That exasperation is probably why he pays less attention to her words as she starts mumbling to herself and more to her hands when he catches a little twitch. They're palm-up on the lap of her pink dress, inched toward him, and her fingers are fidgeting in a manner somewhere between beckoning and grasping the empty air. Is she even aware she's doing that? He mimics the curl in his own hand, hidden by the fold of his arms. His fingers remember that gesture. He's made it before, to her, back on the day Shinra had invaded her church, when he'd jumped the gap in the staircase and was urging her to follow. And now her tone of voice seems similar too, that dominant reassurance (come on, it's fine, you can do it!) with the little bit of desperation that can't be masked (come on, you have to, you're not safe there—!)
"I want to meet…you," she repeats herself, speaking up again, and her voice says she's smiling, and her hands say she knows she's asking him to do something terrifying but she is right here, ready to catch him, if he'll just jump.
It doesn't make sense to him. He can't see the gap. He's right here and obviously reading too much into fidgety fingers, so he lifts his eyes back to her face and waits for a better explanation. But she apparently doesn't have one; and though she never stops smiling, it looks sadder, worried as she shifts further back in her seat for the end of the ride, her hands turning palm-down.
He falls. Hard enough to shatter himself. And by the time he's put back together, she's gone. There was a gap; she just didn't know how to explain it without tripping him up. But she had been trying to protect him all along.
So every time after that, each and every time Cloud sees Aerith's hand reaching for him, he doesn't ask how, or why, or where the gap is. He just jumps.
She's always going to catch him.