"His Majesty originally thought of bringing you here to live with him for a long, long time. Dragons could live as long as they please if they had the motivation. And we thought His Majesty finally found his when he married you. But your heart was never his so he decided to let go. He didn't want to force you to live with him here when you long for someone else."
Alwin explained that Ferdinand was supposed to share his life force with Arabella so she could live much longer than a human could.
As long as Ferdinand continues to supply her with his life force, her body would age slowly and she wouldn't die as long as Ferdinand is alive.
It was how dragons lived with their human mates or other races which had a shorter lifespan.
But since Arabella was in love with Andrew and still longed for him, Ferdinand didn't want to make her live a long life with someone she doesn't like since it would only make her suffer.
